| Message ID | 20241025151128.1854905-1-linux@jordanrome.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] security: add trace event for cap_capable | expand |
On Fri, Oct 25, 2024 at 8:15 AM Jordan Rome <linux@jordanrome.com> wrote: > > In cases where we want a stable way to observe/trace > cap_capable (e.g. protection from inlining and API updates) > add a tracepoint that passes: > - The credentials used > - The user namespace of the resource being accessed > - The user namespace that has the capability to access the > targeted resource > - The capability to check for > - Bitmask of options defined in include/linux/security.h > - The return value of the check > > Signed-off-by: Jordan Rome <linux@jordanrome.com> > --- > MAINTAINERS | 1 + > include/trace/events/capability.h | 60 +++++++++++++++++++++++++++++++ > security/commoncap.c | 31 +++++++++++----- > 3 files changed, 84 insertions(+), 8 deletions(-) > create mode 100644 include/trace/events/capability.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index cc40a9d9b8cd..210e9076c858 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -4994,6 +4994,7 @@ M: Serge Hallyn <serge@hallyn.com> > L: linux-security-module@vger.kernel.org > S: Supported > F: include/linux/capability.h > +F: include/trace/events/capability.h > F: include/uapi/linux/capability.h > F: kernel/capability.c > F: security/commoncap.c > diff --git a/include/trace/events/capability.h b/include/trace/events/capability.h > new file mode 100644 > index 000000000000..e706ce690c38 > --- /dev/null > +++ b/include/trace/events/capability.h > @@ -0,0 +1,60 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#undef TRACE_SYSTEM > +#define TRACE_SYSTEM capability > + > +#if !defined(_TRACE_CAPABILITY_H) || defined(TRACE_HEADER_MULTI_READ) > +#define _TRACE_CAPABILITY_H > + > +#include <linux/cred.h> > +#include <linux/tracepoint.h> > +#include <linux/user_namespace.h> > + > +/** > + * cap_capable - called after it's determined if a task has a particular > + * effective capability > + * > + * @cred: The credentials used > + * @targ_ns: The user namespace of the resource being accessed > + * @capable_ns: The user namespace in which the credential provides the > + * capability to access the targeted resource. > + * This will be NULL if ret is not 0. > + * @cap: The capability to check for > + * @opts: Bitmask of options defined in include/linux/security.h > + * @ret: The return value of the check: 0 if it does, -ve if it does not > + * > + * Allows to trace calls to cap_capable in commoncap.c > + */ > +TRACE_EVENT(cap_capable, > + > + TP_PROTO(const struct cred *cred, struct user_namespace *targ_ns, > + struct user_namespace *capable_ns, int cap, unsigned int opts, int ret), > + > + TP_ARGS(cred, targ_ns, capable_ns, cap, opts, ret), > + > + TP_STRUCT__entry( > + __field(const struct cred *, cred) > + __field(struct user_namespace *, targ_ns) > + __field(struct user_namespace *, capable_ns) > + __field(int, cap) > + __field(unsigned int, opts) > + __field(int, ret) > + ), > + > + TP_fast_assign( > + __entry->cred = cred; > + __entry->targ_ns = targ_ns; > + __entry->capable_ns = capable_ns; > + __entry->cap = cap; > + __entry->opts = opts; > + __entry->ret = ret; > + ), > + > + TP_printk("cred %p, targ_ns %p, capable_ns %p, cap %d, opts %u, ret %d", > + __entry->cred, __entry->targ_ns, __entry->capable_ns, __entry->cap, > + __entry->opts, __entry->ret) > +); > + > +#endif /* _TRACE_CAPABILITY_H */ > + > +/* This part must be outside protection */ > +#include <trace/define_trace.h> > diff --git a/security/commoncap.c b/security/commoncap.c > index 162d96b3a676..12c3ddfe0d6e 100644 > --- a/security/commoncap.c > +++ b/security/commoncap.c > @@ -27,6 +27,9 @@ > #include <linux/mnt_idmapping.h> > #include <uapi/linux/lsm.h> > > +#define CREATE_TRACE_POINTS > +#include <trace/events/capability.h> > + > /* > * If a non-root user executes a setuid-root binary in > * !secure(SECURE_NOROOT) mode, then we raise capabilities. > @@ -52,7 +55,7 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) > /** > * cap_capable - Determine whether a task has a particular effective capability > * @cred: The credentials to use > - * @targ_ns: The user namespace in which we need the capability > + * @targ_ns: The user namespace of the resource being accessed > * @cap: The capability to check for > * @opts: Bitmask of options defined in include/linux/security.h > * > @@ -68,6 +71,7 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > int cap, unsigned int opts) > { > struct user_namespace *ns = targ_ns; > + int ret = -EPERM; > > /* See if cred has the capability in the target user namespace > * by examining the target user namespace and all of the target > @@ -75,22 +79,32 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > */ > for (;;) { > /* Do we have the necessary capabilities? */ > - if (ns == cred->user_ns) > - return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; > + if (ns == cred->user_ns) { > + if (cap_raised(cred->cap_effective, cap)) > + ret = 0; > + else > + ns = NULL; This is a bit unfortunate :( so maybe all we needed was `ns = ns->parent` for that one use case, and keep the original `ret ? NULL : ns` inside trace_cap_capable(). But whatever security folks prefer, I'm fine with either. Acked-by: Andrii Nakryiko <andrii@kernel.org> > + break; > + } > > /* > * If we're already at a lower level than we're looking for, > * we're done searching. > */ > - if (ns->level <= cred->user_ns->level) > - return -EPERM; > + if (ns->level <= cred->user_ns->level) { > + ns = NULL; > + break; > + } > > /* > * The owner of the user namespace in the parent of the > * user namespace has all caps. > */ > - if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) > - return 0; > + if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) { > + ns = ns->parent; > + ret = 0; > + break; > + } > > /* > * If you have a capability in a parent user ns, then you have > @@ -99,7 +113,8 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > ns = ns->parent; > } > > - /* We never get here */ > + trace_cap_capable(cred, targ_ns, ns, cap, opts, ret); > + return ret; > } > > /** > -- > 2.43.5 > >
On Fri, Oct 25, 2024 at 11:37:59AM -0700, Andrii Nakryiko wrote: > On Fri, Oct 25, 2024 at 8:15 AM Jordan Rome <linux@jordanrome.com> wrote: > > > > In cases where we want a stable way to observe/trace > > cap_capable (e.g. protection from inlining and API updates) > > add a tracepoint that passes: > > - The credentials used > > - The user namespace of the resource being accessed > > - The user namespace that has the capability to access the > > targeted resource > > - The capability to check for > > - Bitmask of options defined in include/linux/security.h > > - The return value of the check > > > > Signed-off-by: Jordan Rome <linux@jordanrome.com> > > --- > > MAINTAINERS | 1 + > > include/trace/events/capability.h | 60 +++++++++++++++++++++++++++++++ > > security/commoncap.c | 31 +++++++++++----- > > 3 files changed, 84 insertions(+), 8 deletions(-) > > create mode 100644 include/trace/events/capability.h > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index cc40a9d9b8cd..210e9076c858 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -4994,6 +4994,7 @@ M: Serge Hallyn <serge@hallyn.com> > > L: linux-security-module@vger.kernel.org > > S: Supported > > F: include/linux/capability.h > > +F: include/trace/events/capability.h > > F: include/uapi/linux/capability.h > > F: kernel/capability.c > > F: security/commoncap.c > > diff --git a/include/trace/events/capability.h b/include/trace/events/capability.h > > new file mode 100644 > > index 000000000000..e706ce690c38 > > --- /dev/null > > +++ b/include/trace/events/capability.h > > @@ -0,0 +1,60 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > +#undef TRACE_SYSTEM > > +#define TRACE_SYSTEM capability > > + > > +#if !defined(_TRACE_CAPABILITY_H) || defined(TRACE_HEADER_MULTI_READ) > > +#define _TRACE_CAPABILITY_H > > + > > +#include <linux/cred.h> > > +#include <linux/tracepoint.h> > > +#include <linux/user_namespace.h> > > + > > +/** > > + * cap_capable - called after it's determined if a task has a particular > > + * effective capability > > + * > > + * @cred: The credentials used > > + * @targ_ns: The user namespace of the resource being accessed > > + * @capable_ns: The user namespace in which the credential provides the > > + * capability to access the targeted resource. > > + * This will be NULL if ret is not 0. > > + * @cap: The capability to check for > > + * @opts: Bitmask of options defined in include/linux/security.h > > + * @ret: The return value of the check: 0 if it does, -ve if it does not > > + * > > + * Allows to trace calls to cap_capable in commoncap.c > > + */ > > +TRACE_EVENT(cap_capable, > > + > > + TP_PROTO(const struct cred *cred, struct user_namespace *targ_ns, > > + struct user_namespace *capable_ns, int cap, unsigned int opts, int ret), > > + > > + TP_ARGS(cred, targ_ns, capable_ns, cap, opts, ret), > > + > > + TP_STRUCT__entry( > > + __field(const struct cred *, cred) > > + __field(struct user_namespace *, targ_ns) > > + __field(struct user_namespace *, capable_ns) > > + __field(int, cap) > > + __field(unsigned int, opts) > > + __field(int, ret) > > + ), > > + > > + TP_fast_assign( > > + __entry->cred = cred; > > + __entry->targ_ns = targ_ns; > > + __entry->capable_ns = capable_ns; > > + __entry->cap = cap; > > + __entry->opts = opts; > > + __entry->ret = ret; > > + ), > > + > > + TP_printk("cred %p, targ_ns %p, capable_ns %p, cap %d, opts %u, ret %d", > > + __entry->cred, __entry->targ_ns, __entry->capable_ns, __entry->cap, > > + __entry->opts, __entry->ret) > > +); > > + > > +#endif /* _TRACE_CAPABILITY_H */ > > + > > +/* This part must be outside protection */ > > +#include <trace/define_trace.h> > > diff --git a/security/commoncap.c b/security/commoncap.c > > index 162d96b3a676..12c3ddfe0d6e 100644 > > --- a/security/commoncap.c > > +++ b/security/commoncap.c > > @@ -27,6 +27,9 @@ > > #include <linux/mnt_idmapping.h> > > #include <uapi/linux/lsm.h> > > > > +#define CREATE_TRACE_POINTS > > +#include <trace/events/capability.h> > > + > > /* > > * If a non-root user executes a setuid-root binary in > > * !secure(SECURE_NOROOT) mode, then we raise capabilities. > > @@ -52,7 +55,7 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) > > /** > > * cap_capable - Determine whether a task has a particular effective capability > > * @cred: The credentials to use > > - * @targ_ns: The user namespace in which we need the capability > > + * @targ_ns: The user namespace of the resource being accessed > > * @cap: The capability to check for > > * @opts: Bitmask of options defined in include/linux/security.h > > * > > @@ -68,6 +71,7 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > int cap, unsigned int opts) > > { > > struct user_namespace *ns = targ_ns; > > + int ret = -EPERM; > > > > /* See if cred has the capability in the target user namespace > > * by examining the target user namespace and all of the target > > @@ -75,22 +79,32 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > */ > > for (;;) { > > /* Do we have the necessary capabilities? */ > > - if (ns == cred->user_ns) > > - return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; > > + if (ns == cred->user_ns) { > > + if (cap_raised(cred->cap_effective, cap)) > > + ret = 0; > > + else > > + ns = NULL; > > This is a bit unfortunate :( so maybe all we needed was `ns = > ns->parent` for that one use case, and keep the original `ret ? NULL : > ns` inside trace_cap_capable(). Yeah, that would be fine with me. Or maybe just doing /* in case of an error, trace should show ns=NULL */ if (ret) ns = NULL; right above the trace_cap_capable() call would be clearer. > But whatever security folks prefer, I'm fine with either. > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > > > + break; > > + } > > > > /* > > * If we're already at a lower level than we're looking for, > > * we're done searching. > > */ > > - if (ns->level <= cred->user_ns->level) > > - return -EPERM; > > + if (ns->level <= cred->user_ns->level) { > > + ns = NULL; > > + break; > > + } > > > > /* > > * The owner of the user namespace in the parent of the > > * user namespace has all caps. > > */ > > - if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) > > - return 0; > > + if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) { > > + ns = ns->parent; > > + ret = 0; > > + break; > > + } > > > > /* > > * If you have a capability in a parent user ns, then you have > > @@ -99,7 +113,8 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > ns = ns->parent; > > } > > > > - /* We never get here */ > > + trace_cap_capable(cred, targ_ns, ns, cap, opts, ret); > > + return ret; > > } > > > > /** > > -- > > 2.43.5 > > > >
On Fri, Oct 25, 2024 at 3:52 PM Serge E. Hallyn <serge@hallyn.com> wrote: > > On Fri, Oct 25, 2024 at 11:37:59AM -0700, Andrii Nakryiko wrote: > > On Fri, Oct 25, 2024 at 8:15 AM Jordan Rome <linux@jordanrome.com> wrote: > > > > > > In cases where we want a stable way to observe/trace > > > cap_capable (e.g. protection from inlining and API updates) > > > add a tracepoint that passes: > > > - The credentials used > > > - The user namespace of the resource being accessed > > > - The user namespace that has the capability to access the > > > targeted resource > > > - The capability to check for > > > - Bitmask of options defined in include/linux/security.h > > > - The return value of the check > > > > > > Signed-off-by: Jordan Rome <linux@jordanrome.com> > > > --- > > > MAINTAINERS | 1 + > > > include/trace/events/capability.h | 60 +++++++++++++++++++++++++++++++ > > > security/commoncap.c | 31 +++++++++++----- > > > 3 files changed, 84 insertions(+), 8 deletions(-) > > > create mode 100644 include/trace/events/capability.h > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > index cc40a9d9b8cd..210e9076c858 100644 > > > --- a/MAINTAINERS > > > +++ b/MAINTAINERS > > > @@ -4994,6 +4994,7 @@ M: Serge Hallyn <serge@hallyn.com> > > > L: linux-security-module@vger.kernel.org > > > S: Supported > > > F: include/linux/capability.h > > > +F: include/trace/events/capability.h > > > F: include/uapi/linux/capability.h > > > F: kernel/capability.c > > > F: security/commoncap.c > > > diff --git a/include/trace/events/capability.h b/include/trace/events/capability.h > > > new file mode 100644 > > > index 000000000000..e706ce690c38 > > > --- /dev/null > > > +++ b/include/trace/events/capability.h > > > @@ -0,0 +1,60 @@ > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > +#undef TRACE_SYSTEM > > > +#define TRACE_SYSTEM capability > > > + > > > +#if !defined(_TRACE_CAPABILITY_H) || defined(TRACE_HEADER_MULTI_READ) > > > +#define _TRACE_CAPABILITY_H > > > + > > > +#include <linux/cred.h> > > > +#include <linux/tracepoint.h> > > > +#include <linux/user_namespace.h> > > > + > > > +/** > > > + * cap_capable - called after it's determined if a task has a particular > > > + * effective capability > > > + * > > > + * @cred: The credentials used > > > + * @targ_ns: The user namespace of the resource being accessed > > > + * @capable_ns: The user namespace in which the credential provides the > > > + * capability to access the targeted resource. > > > + * This will be NULL if ret is not 0. > > > + * @cap: The capability to check for > > > + * @opts: Bitmask of options defined in include/linux/security.h > > > + * @ret: The return value of the check: 0 if it does, -ve if it does not > > > + * > > > + * Allows to trace calls to cap_capable in commoncap.c > > > + */ > > > +TRACE_EVENT(cap_capable, > > > + > > > + TP_PROTO(const struct cred *cred, struct user_namespace *targ_ns, > > > + struct user_namespace *capable_ns, int cap, unsigned int opts, int ret), > > > + > > > + TP_ARGS(cred, targ_ns, capable_ns, cap, opts, ret), > > > + > > > + TP_STRUCT__entry( > > > + __field(const struct cred *, cred) > > > + __field(struct user_namespace *, targ_ns) > > > + __field(struct user_namespace *, capable_ns) > > > + __field(int, cap) > > > + __field(unsigned int, opts) > > > + __field(int, ret) > > > + ), > > > + > > > + TP_fast_assign( > > > + __entry->cred = cred; > > > + __entry->targ_ns = targ_ns; > > > + __entry->capable_ns = capable_ns; > > > + __entry->cap = cap; > > > + __entry->opts = opts; > > > + __entry->ret = ret; > > > + ), > > > + > > > + TP_printk("cred %p, targ_ns %p, capable_ns %p, cap %d, opts %u, ret %d", > > > + __entry->cred, __entry->targ_ns, __entry->capable_ns, __entry->cap, > > > + __entry->opts, __entry->ret) > > > +); > > > + > > > +#endif /* _TRACE_CAPABILITY_H */ > > > + > > > +/* This part must be outside protection */ > > > +#include <trace/define_trace.h> > > > diff --git a/security/commoncap.c b/security/commoncap.c > > > index 162d96b3a676..12c3ddfe0d6e 100644 > > > --- a/security/commoncap.c > > > +++ b/security/commoncap.c > > > @@ -27,6 +27,9 @@ > > > #include <linux/mnt_idmapping.h> > > > #include <uapi/linux/lsm.h> > > > > > > +#define CREATE_TRACE_POINTS > > > +#include <trace/events/capability.h> > > > + > > > /* > > > * If a non-root user executes a setuid-root binary in > > > * !secure(SECURE_NOROOT) mode, then we raise capabilities. > > > @@ -52,7 +55,7 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) > > > /** > > > * cap_capable - Determine whether a task has a particular effective capability > > > * @cred: The credentials to use > > > - * @targ_ns: The user namespace in which we need the capability > > > + * @targ_ns: The user namespace of the resource being accessed > > > * @cap: The capability to check for > > > * @opts: Bitmask of options defined in include/linux/security.h > > > * > > > @@ -68,6 +71,7 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > int cap, unsigned int opts) > > > { > > > struct user_namespace *ns = targ_ns; > > > + int ret = -EPERM; > > > > > > /* See if cred has the capability in the target user namespace > > > * by examining the target user namespace and all of the target > > > @@ -75,22 +79,32 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > */ > > > for (;;) { > > > /* Do we have the necessary capabilities? */ > > > - if (ns == cred->user_ns) > > > - return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; > > > + if (ns == cred->user_ns) { > > > + if (cap_raised(cred->cap_effective, cap)) > > > + ret = 0; > > > + else > > > + ns = NULL; > > > > This is a bit unfortunate :( so maybe all we needed was `ns = > > ns->parent` for that one use case, and keep the original `ret ? NULL : > > ns` inside trace_cap_capable(). > > Yeah, that would be fine with me. Or maybe just doing > > /* in case of an error, trace should show ns=NULL */ > if (ret) > ns = NULL; > > right above the trace_cap_capable() call would be clearer. I feel like having less trace specific logic in this function would be a good thing, so I'm for Andrii's suggestion of doing the ret check there but also fine to do what security folks prefer :) > > > But whatever security folks prefer, I'm fine with either. > > > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > > > > > + break; > > > + } > > > > > > /* > > > * If we're already at a lower level than we're looking for, > > > * we're done searching. > > > */ > > > - if (ns->level <= cred->user_ns->level) > > > - return -EPERM; > > > + if (ns->level <= cred->user_ns->level) { > > > + ns = NULL; > > > + break; > > > + } > > > > > > /* > > > * The owner of the user namespace in the parent of the > > > * user namespace has all caps. > > > */ > > > - if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) > > > - return 0; > > > + if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) { > > > + ns = ns->parent; > > > + ret = 0; > > > + break; > > > + } > > > > > > /* > > > * If you have a capability in a parent user ns, then you have > > > @@ -99,7 +113,8 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > ns = ns->parent; > > > } > > > > > > - /* We never get here */ > > > + trace_cap_capable(cred, targ_ns, ns, cap, opts, ret); > > > + return ret; > > > } > > > > > > /** > > > -- > > > 2.43.5 > > > > > >
On Fri, Oct 25, 2024 at 04:24:05PM -0400, Jordan Rome wrote: > On Fri, Oct 25, 2024 at 3:52 PM Serge E. Hallyn <serge@hallyn.com> wrote: > > > > On Fri, Oct 25, 2024 at 11:37:59AM -0700, Andrii Nakryiko wrote: > > > On Fri, Oct 25, 2024 at 8:15 AM Jordan Rome <linux@jordanrome.com> wrote: > > > > > > > > In cases where we want a stable way to observe/trace > > > > cap_capable (e.g. protection from inlining and API updates) > > > > add a tracepoint that passes: > > > > - The credentials used > > > > - The user namespace of the resource being accessed > > > > - The user namespace that has the capability to access the > > > > targeted resource > > > > - The capability to check for > > > > - Bitmask of options defined in include/linux/security.h > > > > - The return value of the check > > > > > > > > Signed-off-by: Jordan Rome <linux@jordanrome.com> > > > > --- > > > > MAINTAINERS | 1 + > > > > include/trace/events/capability.h | 60 +++++++++++++++++++++++++++++++ > > > > security/commoncap.c | 31 +++++++++++----- > > > > 3 files changed, 84 insertions(+), 8 deletions(-) > > > > create mode 100644 include/trace/events/capability.h > > > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > > index cc40a9d9b8cd..210e9076c858 100644 > > > > --- a/MAINTAINERS > > > > +++ b/MAINTAINERS > > > > @@ -4994,6 +4994,7 @@ M: Serge Hallyn <serge@hallyn.com> > > > > L: linux-security-module@vger.kernel.org > > > > S: Supported > > > > F: include/linux/capability.h > > > > +F: include/trace/events/capability.h > > > > F: include/uapi/linux/capability.h > > > > F: kernel/capability.c > > > > F: security/commoncap.c > > > > diff --git a/include/trace/events/capability.h b/include/trace/events/capability.h > > > > new file mode 100644 > > > > index 000000000000..e706ce690c38 > > > > --- /dev/null > > > > +++ b/include/trace/events/capability.h > > > > @@ -0,0 +1,60 @@ > > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > > +#undef TRACE_SYSTEM > > > > +#define TRACE_SYSTEM capability > > > > + > > > > +#if !defined(_TRACE_CAPABILITY_H) || defined(TRACE_HEADER_MULTI_READ) > > > > +#define _TRACE_CAPABILITY_H > > > > + > > > > +#include <linux/cred.h> > > > > +#include <linux/tracepoint.h> > > > > +#include <linux/user_namespace.h> > > > > + > > > > +/** > > > > + * cap_capable - called after it's determined if a task has a particular > > > > + * effective capability > > > > + * > > > > + * @cred: The credentials used > > > > + * @targ_ns: The user namespace of the resource being accessed > > > > + * @capable_ns: The user namespace in which the credential provides the > > > > + * capability to access the targeted resource. > > > > + * This will be NULL if ret is not 0. > > > > + * @cap: The capability to check for > > > > + * @opts: Bitmask of options defined in include/linux/security.h > > > > + * @ret: The return value of the check: 0 if it does, -ve if it does not > > > > + * > > > > + * Allows to trace calls to cap_capable in commoncap.c > > > > + */ > > > > +TRACE_EVENT(cap_capable, > > > > + > > > > + TP_PROTO(const struct cred *cred, struct user_namespace *targ_ns, > > > > + struct user_namespace *capable_ns, int cap, unsigned int opts, int ret), > > > > + > > > > + TP_ARGS(cred, targ_ns, capable_ns, cap, opts, ret), > > > > + > > > > + TP_STRUCT__entry( > > > > + __field(const struct cred *, cred) > > > > + __field(struct user_namespace *, targ_ns) > > > > + __field(struct user_namespace *, capable_ns) > > > > + __field(int, cap) > > > > + __field(unsigned int, opts) > > > > + __field(int, ret) > > > > + ), > > > > + > > > > + TP_fast_assign( > > > > + __entry->cred = cred; > > > > + __entry->targ_ns = targ_ns; > > > > + __entry->capable_ns = capable_ns; > > > > + __entry->cap = cap; > > > > + __entry->opts = opts; > > > > + __entry->ret = ret; > > > > + ), > > > > + > > > > + TP_printk("cred %p, targ_ns %p, capable_ns %p, cap %d, opts %u, ret %d", > > > > + __entry->cred, __entry->targ_ns, __entry->capable_ns, __entry->cap, > > > > + __entry->opts, __entry->ret) > > > > +); > > > > + > > > > +#endif /* _TRACE_CAPABILITY_H */ > > > > + > > > > +/* This part must be outside protection */ > > > > +#include <trace/define_trace.h> > > > > diff --git a/security/commoncap.c b/security/commoncap.c > > > > index 162d96b3a676..12c3ddfe0d6e 100644 > > > > --- a/security/commoncap.c > > > > +++ b/security/commoncap.c > > > > @@ -27,6 +27,9 @@ > > > > #include <linux/mnt_idmapping.h> > > > > #include <uapi/linux/lsm.h> > > > > > > > > +#define CREATE_TRACE_POINTS > > > > +#include <trace/events/capability.h> > > > > + > > > > /* > > > > * If a non-root user executes a setuid-root binary in > > > > * !secure(SECURE_NOROOT) mode, then we raise capabilities. > > > > @@ -52,7 +55,7 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) > > > > /** > > > > * cap_capable - Determine whether a task has a particular effective capability > > > > * @cred: The credentials to use > > > > - * @targ_ns: The user namespace in which we need the capability > > > > + * @targ_ns: The user namespace of the resource being accessed > > > > * @cap: The capability to check for > > > > * @opts: Bitmask of options defined in include/linux/security.h > > > > * > > > > @@ -68,6 +71,7 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > > int cap, unsigned int opts) > > > > { > > > > struct user_namespace *ns = targ_ns; > > > > + int ret = -EPERM; > > > > > > > > /* See if cred has the capability in the target user namespace > > > > * by examining the target user namespace and all of the target > > > > @@ -75,22 +79,32 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > > */ > > > > for (;;) { > > > > /* Do we have the necessary capabilities? */ > > > > - if (ns == cred->user_ns) > > > > - return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; > > > > + if (ns == cred->user_ns) { > > > > + if (cap_raised(cred->cap_effective, cap)) > > > > + ret = 0; > > > > + else > > > > + ns = NULL; > > > > > > This is a bit unfortunate :( so maybe all we needed was `ns = > > > ns->parent` for that one use case, and keep the original `ret ? NULL : > > > ns` inside trace_cap_capable(). > > > > Yeah, that would be fine with me. Or maybe just doing > > > > /* in case of an error, trace should show ns=NULL */ > > if (ret) > > ns = NULL; > > > > right above the trace_cap_capable() call would be clearer. > > I feel like having less trace specific logic in this function would be > a good thing, > so I'm for Andrii's suggestion of doing the ret check there but also > fine to do what security folks prefer :) I think a comment is needed to remind us (me) in 2 years why the seting of ns to NULL is there. But the comment of trace_cap_capable() probably suffices, so sure, go with Andrii's suggestion. And then Reviewed-by: Serge Hallyn <serge@hallyn.com> for the capability code. thanks, -serge
On Sat, Oct 26, 2024 at 6:10 AM Serge E. Hallyn <serge@hallyn.com> wrote: > > On Fri, Oct 25, 2024 at 04:24:05PM -0400, Jordan Rome wrote: > > On Fri, Oct 25, 2024 at 3:52 PM Serge E. Hallyn <serge@hallyn.com> wrote: > > > > > > On Fri, Oct 25, 2024 at 11:37:59AM -0700, Andrii Nakryiko wrote: > > > > On Fri, Oct 25, 2024 at 8:15 AM Jordan Rome <linux@jordanrome.com> wrote: > > > > > > > > > > In cases where we want a stable way to observe/trace > > > > > cap_capable (e.g. protection from inlining and API updates) > > > > > add a tracepoint that passes: > > > > > - The credentials used > > > > > - The user namespace of the resource being accessed > > > > > - The user namespace that has the capability to access the > > > > > targeted resource > > > > > - The capability to check for > > > > > - Bitmask of options defined in include/linux/security.h > > > > > - The return value of the check > > > > > > > > > > Signed-off-by: Jordan Rome <linux@jordanrome.com> > > > > > --- > > > > > MAINTAINERS | 1 + > > > > > include/trace/events/capability.h | 60 +++++++++++++++++++++++++++++++ > > > > > security/commoncap.c | 31 +++++++++++----- > > > > > 3 files changed, 84 insertions(+), 8 deletions(-) > > > > > create mode 100644 include/trace/events/capability.h > > > > > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > > > index cc40a9d9b8cd..210e9076c858 100644 > > > > > --- a/MAINTAINERS > > > > > +++ b/MAINTAINERS > > > > > @@ -4994,6 +4994,7 @@ M: Serge Hallyn <serge@hallyn.com> > > > > > L: linux-security-module@vger.kernel.org > > > > > S: Supported > > > > > F: include/linux/capability.h > > > > > +F: include/trace/events/capability.h > > > > > F: include/uapi/linux/capability.h > > > > > F: kernel/capability.c > > > > > F: security/commoncap.c > > > > > diff --git a/include/trace/events/capability.h b/include/trace/events/capability.h > > > > > new file mode 100644 > > > > > index 000000000000..e706ce690c38 > > > > > --- /dev/null > > > > > +++ b/include/trace/events/capability.h > > > > > @@ -0,0 +1,60 @@ > > > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > > > +#undef TRACE_SYSTEM > > > > > +#define TRACE_SYSTEM capability > > > > > + > > > > > +#if !defined(_TRACE_CAPABILITY_H) || defined(TRACE_HEADER_MULTI_READ) > > > > > +#define _TRACE_CAPABILITY_H > > > > > + > > > > > +#include <linux/cred.h> > > > > > +#include <linux/tracepoint.h> > > > > > +#include <linux/user_namespace.h> > > > > > + > > > > > +/** > > > > > + * cap_capable - called after it's determined if a task has a particular > > > > > + * effective capability > > > > > + * > > > > > + * @cred: The credentials used > > > > > + * @targ_ns: The user namespace of the resource being accessed > > > > > + * @capable_ns: The user namespace in which the credential provides the > > > > > + * capability to access the targeted resource. > > > > > + * This will be NULL if ret is not 0. > > > > > + * @cap: The capability to check for > > > > > + * @opts: Bitmask of options defined in include/linux/security.h > > > > > + * @ret: The return value of the check: 0 if it does, -ve if it does not > > > > > + * > > > > > + * Allows to trace calls to cap_capable in commoncap.c > > > > > + */ > > > > > +TRACE_EVENT(cap_capable, > > > > > + > > > > > + TP_PROTO(const struct cred *cred, struct user_namespace *targ_ns, > > > > > + struct user_namespace *capable_ns, int cap, unsigned int opts, int ret), > > > > > + > > > > > + TP_ARGS(cred, targ_ns, capable_ns, cap, opts, ret), > > > > > + > > > > > + TP_STRUCT__entry( > > > > > + __field(const struct cred *, cred) > > > > > + __field(struct user_namespace *, targ_ns) > > > > > + __field(struct user_namespace *, capable_ns) > > > > > + __field(int, cap) > > > > > + __field(unsigned int, opts) > > > > > + __field(int, ret) > > > > > + ), > > > > > + > > > > > + TP_fast_assign( > > > > > + __entry->cred = cred; > > > > > + __entry->targ_ns = targ_ns; > > > > > + __entry->capable_ns = capable_ns; > > > > > + __entry->cap = cap; > > > > > + __entry->opts = opts; > > > > > + __entry->ret = ret; > > > > > + ), > > > > > + > > > > > + TP_printk("cred %p, targ_ns %p, capable_ns %p, cap %d, opts %u, ret %d", > > > > > + __entry->cred, __entry->targ_ns, __entry->capable_ns, __entry->cap, > > > > > + __entry->opts, __entry->ret) > > > > > +); > > > > > + > > > > > +#endif /* _TRACE_CAPABILITY_H */ > > > > > + > > > > > +/* This part must be outside protection */ > > > > > +#include <trace/define_trace.h> > > > > > diff --git a/security/commoncap.c b/security/commoncap.c > > > > > index 162d96b3a676..12c3ddfe0d6e 100644 > > > > > --- a/security/commoncap.c > > > > > +++ b/security/commoncap.c > > > > > @@ -27,6 +27,9 @@ > > > > > #include <linux/mnt_idmapping.h> > > > > > #include <uapi/linux/lsm.h> > > > > > > > > > > +#define CREATE_TRACE_POINTS > > > > > +#include <trace/events/capability.h> > > > > > + > > > > > /* > > > > > * If a non-root user executes a setuid-root binary in > > > > > * !secure(SECURE_NOROOT) mode, then we raise capabilities. > > > > > @@ -52,7 +55,7 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) > > > > > /** > > > > > * cap_capable - Determine whether a task has a particular effective capability > > > > > * @cred: The credentials to use > > > > > - * @targ_ns: The user namespace in which we need the capability > > > > > + * @targ_ns: The user namespace of the resource being accessed > > > > > * @cap: The capability to check for > > > > > * @opts: Bitmask of options defined in include/linux/security.h > > > > > * > > > > > @@ -68,6 +71,7 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > > > int cap, unsigned int opts) > > > > > { > > > > > struct user_namespace *ns = targ_ns; > > > > > + int ret = -EPERM; > > > > > > > > > > /* See if cred has the capability in the target user namespace > > > > > * by examining the target user namespace and all of the target > > > > > @@ -75,22 +79,32 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > > > */ > > > > > for (;;) { > > > > > /* Do we have the necessary capabilities? */ > > > > > - if (ns == cred->user_ns) > > > > > - return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; > > > > > + if (ns == cred->user_ns) { > > > > > + if (cap_raised(cred->cap_effective, cap)) > > > > > + ret = 0; > > > > > + else > > > > > + ns = NULL; > > > > > > > > This is a bit unfortunate :( so maybe all we needed was `ns = > > > > ns->parent` for that one use case, and keep the original `ret ? NULL : > > > > ns` inside trace_cap_capable(). > > > > > > Yeah, that would be fine with me. Or maybe just doing > > > > > > /* in case of an error, trace should show ns=NULL */ > > > if (ret) > > > ns = NULL; > > > > > > right above the trace_cap_capable() call would be clearer. > > > > I feel like having less trace specific logic in this function would be > > a good thing, > > so I'm for Andrii's suggestion of doing the ret check there but also > > fine to do what security folks prefer :) > > I think a comment is needed to remind us (me) in 2 years why the > seting of ns to NULL is there. But the comment of trace_cap_capable() > probably suffices, so sure, go with Andrii's suggestion. And then > > Reviewed-by: Serge Hallyn <serge@hallyn.com> > > for the capability code. > > thanks, > -serge I think we're suggesting to not set ns = NULL here and instead check the ret value in the trace code e.g. `__entry->capable_ns = ret ? NULL : capable_ns;` I think the only trace-specific thing, which I can add a comment for, is this part `ns = ns->parent;` after we already set the ret to 0.
On Sat, Oct 26, 2024 at 07:22:29AM -0400, Jordan Rome wrote: > On Sat, Oct 26, 2024 at 6:10 AM Serge E. Hallyn <serge@hallyn.com> wrote: > > > > On Fri, Oct 25, 2024 at 04:24:05PM -0400, Jordan Rome wrote: > > > On Fri, Oct 25, 2024 at 3:52 PM Serge E. Hallyn <serge@hallyn.com> wrote: > > > > > > > > On Fri, Oct 25, 2024 at 11:37:59AM -0700, Andrii Nakryiko wrote: > > > > > On Fri, Oct 25, 2024 at 8:15 AM Jordan Rome <linux@jordanrome.com> wrote: > > > > > > > > > > > > In cases where we want a stable way to observe/trace > > > > > > cap_capable (e.g. protection from inlining and API updates) > > > > > > add a tracepoint that passes: > > > > > > - The credentials used > > > > > > - The user namespace of the resource being accessed > > > > > > - The user namespace that has the capability to access the > > > > > > targeted resource > > > > > > - The capability to check for > > > > > > - Bitmask of options defined in include/linux/security.h > > > > > > - The return value of the check > > > > > > > > > > > > Signed-off-by: Jordan Rome <linux@jordanrome.com> > > > > > > --- > > > > > > MAINTAINERS | 1 + > > > > > > include/trace/events/capability.h | 60 +++++++++++++++++++++++++++++++ > > > > > > security/commoncap.c | 31 +++++++++++----- > > > > > > 3 files changed, 84 insertions(+), 8 deletions(-) > > > > > > create mode 100644 include/trace/events/capability.h > > > > > > > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > > > > index cc40a9d9b8cd..210e9076c858 100644 > > > > > > --- a/MAINTAINERS > > > > > > +++ b/MAINTAINERS > > > > > > @@ -4994,6 +4994,7 @@ M: Serge Hallyn <serge@hallyn.com> > > > > > > L: linux-security-module@vger.kernel.org > > > > > > S: Supported > > > > > > F: include/linux/capability.h > > > > > > +F: include/trace/events/capability.h > > > > > > F: include/uapi/linux/capability.h > > > > > > F: kernel/capability.c > > > > > > F: security/commoncap.c > > > > > > diff --git a/include/trace/events/capability.h b/include/trace/events/capability.h > > > > > > new file mode 100644 > > > > > > index 000000000000..e706ce690c38 > > > > > > --- /dev/null > > > > > > +++ b/include/trace/events/capability.h > > > > > > @@ -0,0 +1,60 @@ > > > > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > > > > +#undef TRACE_SYSTEM > > > > > > +#define TRACE_SYSTEM capability > > > > > > + > > > > > > +#if !defined(_TRACE_CAPABILITY_H) || defined(TRACE_HEADER_MULTI_READ) > > > > > > +#define _TRACE_CAPABILITY_H > > > > > > + > > > > > > +#include <linux/cred.h> > > > > > > +#include <linux/tracepoint.h> > > > > > > +#include <linux/user_namespace.h> > > > > > > + > > > > > > +/** > > > > > > + * cap_capable - called after it's determined if a task has a particular > > > > > > + * effective capability > > > > > > + * > > > > > > + * @cred: The credentials used > > > > > > + * @targ_ns: The user namespace of the resource being accessed > > > > > > + * @capable_ns: The user namespace in which the credential provides the > > > > > > + * capability to access the targeted resource. > > > > > > + * This will be NULL if ret is not 0. > > > > > > + * @cap: The capability to check for > > > > > > + * @opts: Bitmask of options defined in include/linux/security.h > > > > > > + * @ret: The return value of the check: 0 if it does, -ve if it does not > > > > > > + * > > > > > > + * Allows to trace calls to cap_capable in commoncap.c > > > > > > + */ > > > > > > +TRACE_EVENT(cap_capable, > > > > > > + > > > > > > + TP_PROTO(const struct cred *cred, struct user_namespace *targ_ns, > > > > > > + struct user_namespace *capable_ns, int cap, unsigned int opts, int ret), > > > > > > + > > > > > > + TP_ARGS(cred, targ_ns, capable_ns, cap, opts, ret), > > > > > > + > > > > > > + TP_STRUCT__entry( > > > > > > + __field(const struct cred *, cred) > > > > > > + __field(struct user_namespace *, targ_ns) > > > > > > + __field(struct user_namespace *, capable_ns) > > > > > > + __field(int, cap) > > > > > > + __field(unsigned int, opts) > > > > > > + __field(int, ret) > > > > > > + ), > > > > > > + > > > > > > + TP_fast_assign( > > > > > > + __entry->cred = cred; > > > > > > + __entry->targ_ns = targ_ns; > > > > > > + __entry->capable_ns = capable_ns; > > > > > > + __entry->cap = cap; > > > > > > + __entry->opts = opts; > > > > > > + __entry->ret = ret; > > > > > > + ), > > > > > > + > > > > > > + TP_printk("cred %p, targ_ns %p, capable_ns %p, cap %d, opts %u, ret %d", > > > > > > + __entry->cred, __entry->targ_ns, __entry->capable_ns, __entry->cap, > > > > > > + __entry->opts, __entry->ret) > > > > > > +); > > > > > > + > > > > > > +#endif /* _TRACE_CAPABILITY_H */ > > > > > > + > > > > > > +/* This part must be outside protection */ > > > > > > +#include <trace/define_trace.h> > > > > > > diff --git a/security/commoncap.c b/security/commoncap.c > > > > > > index 162d96b3a676..12c3ddfe0d6e 100644 > > > > > > --- a/security/commoncap.c > > > > > > +++ b/security/commoncap.c > > > > > > @@ -27,6 +27,9 @@ > > > > > > #include <linux/mnt_idmapping.h> > > > > > > #include <uapi/linux/lsm.h> > > > > > > > > > > > > +#define CREATE_TRACE_POINTS > > > > > > +#include <trace/events/capability.h> > > > > > > + > > > > > > /* > > > > > > * If a non-root user executes a setuid-root binary in > > > > > > * !secure(SECURE_NOROOT) mode, then we raise capabilities. > > > > > > @@ -52,7 +55,7 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) > > > > > > /** > > > > > > * cap_capable - Determine whether a task has a particular effective capability > > > > > > * @cred: The credentials to use > > > > > > - * @targ_ns: The user namespace in which we need the capability > > > > > > + * @targ_ns: The user namespace of the resource being accessed > > > > > > * @cap: The capability to check for > > > > > > * @opts: Bitmask of options defined in include/linux/security.h > > > > > > * > > > > > > @@ -68,6 +71,7 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > > > > int cap, unsigned int opts) > > > > > > { > > > > > > struct user_namespace *ns = targ_ns; > > > > > > + int ret = -EPERM; > > > > > > > > > > > > /* See if cred has the capability in the target user namespace > > > > > > * by examining the target user namespace and all of the target > > > > > > @@ -75,22 +79,32 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > > > > */ > > > > > > for (;;) { > > > > > > /* Do we have the necessary capabilities? */ > > > > > > - if (ns == cred->user_ns) > > > > > > - return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; > > > > > > + if (ns == cred->user_ns) { > > > > > > + if (cap_raised(cred->cap_effective, cap)) > > > > > > + ret = 0; > > > > > > + else > > > > > > + ns = NULL; > > > > > > > > > > This is a bit unfortunate :( so maybe all we needed was `ns = > > > > > ns->parent` for that one use case, and keep the original `ret ? NULL : > > > > > ns` inside trace_cap_capable(). > > > > > > > > Yeah, that would be fine with me. Or maybe just doing > > > > > > > > /* in case of an error, trace should show ns=NULL */ > > > > if (ret) > > > > ns = NULL; > > > > > > > > right above the trace_cap_capable() call would be clearer. > > > > > > I feel like having less trace specific logic in this function would be > > > a good thing, > > > so I'm for Andrii's suggestion of doing the ret check there but also > > > fine to do what security folks prefer :) > > > > I think a comment is needed to remind us (me) in 2 years why the > > seting of ns to NULL is there. But the comment of trace_cap_capable() > > probably suffices, so sure, go with Andrii's suggestion. And then > > > > Reviewed-by: Serge Hallyn <serge@hallyn.com> > > > > for the capability code. > > > > thanks, > > -serge > > I think we're suggesting to not set ns = NULL here and instead > check the ret value in the trace code e.g. > `__entry->capable_ns = ret ? NULL : capable_ns;` Perfect. Was originally going to suggest this, but then thought well the rest of the ns logic is purely capability not tracing related. But since the comment is in trace_cap_capable(), putting the assignment there makes sense. > I think the only trace-specific thing, which I can add a comment > for, is this part `ns = ns->parent;` after we already set the ret to 0.
On Sat, Oct 26, 2024 at 9:00 AM Serge E. Hallyn <serge@hallyn.com> wrote: > > On Sat, Oct 26, 2024 at 07:22:29AM -0400, Jordan Rome wrote: > > On Sat, Oct 26, 2024 at 6:10 AM Serge E. Hallyn <serge@hallyn.com> wrote: > > > > > > On Fri, Oct 25, 2024 at 04:24:05PM -0400, Jordan Rome wrote: > > > > On Fri, Oct 25, 2024 at 3:52 PM Serge E. Hallyn <serge@hallyn.com> wrote: > > > > > > > > > > On Fri, Oct 25, 2024 at 11:37:59AM -0700, Andrii Nakryiko wrote: > > > > > > On Fri, Oct 25, 2024 at 8:15 AM Jordan Rome <linux@jordanrome.com> wrote: > > > > > > > > > > > > > > In cases where we want a stable way to observe/trace > > > > > > > cap_capable (e.g. protection from inlining and API updates) > > > > > > > add a tracepoint that passes: > > > > > > > - The credentials used > > > > > > > - The user namespace of the resource being accessed > > > > > > > - The user namespace that has the capability to access the > > > > > > > targeted resource > > > > > > > - The capability to check for > > > > > > > - Bitmask of options defined in include/linux/security.h > > > > > > > - The return value of the check > > > > > > > > > > > > > > Signed-off-by: Jordan Rome <linux@jordanrome.com> > > > > > > > --- > > > > > > > MAINTAINERS | 1 + > > > > > > > include/trace/events/capability.h | 60 +++++++++++++++++++++++++++++++ > > > > > > > security/commoncap.c | 31 +++++++++++----- > > > > > > > 3 files changed, 84 insertions(+), 8 deletions(-) > > > > > > > create mode 100644 include/trace/events/capability.h > > > > > > > > > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > > > > > index cc40a9d9b8cd..210e9076c858 100644 > > > > > > > --- a/MAINTAINERS > > > > > > > +++ b/MAINTAINERS > > > > > > > @@ -4994,6 +4994,7 @@ M: Serge Hallyn <serge@hallyn.com> > > > > > > > L: linux-security-module@vger.kernel.org > > > > > > > S: Supported > > > > > > > F: include/linux/capability.h > > > > > > > +F: include/trace/events/capability.h > > > > > > > F: include/uapi/linux/capability.h > > > > > > > F: kernel/capability.c > > > > > > > F: security/commoncap.c > > > > > > > diff --git a/include/trace/events/capability.h b/include/trace/events/capability.h > > > > > > > new file mode 100644 > > > > > > > index 000000000000..e706ce690c38 > > > > > > > --- /dev/null > > > > > > > +++ b/include/trace/events/capability.h > > > > > > > @@ -0,0 +1,60 @@ > > > > > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > > > > > +#undef TRACE_SYSTEM > > > > > > > +#define TRACE_SYSTEM capability > > > > > > > + > > > > > > > +#if !defined(_TRACE_CAPABILITY_H) || defined(TRACE_HEADER_MULTI_READ) > > > > > > > +#define _TRACE_CAPABILITY_H > > > > > > > + > > > > > > > +#include <linux/cred.h> > > > > > > > +#include <linux/tracepoint.h> > > > > > > > +#include <linux/user_namespace.h> > > > > > > > + > > > > > > > +/** > > > > > > > + * cap_capable - called after it's determined if a task has a particular > > > > > > > + * effective capability > > > > > > > + * > > > > > > > + * @cred: The credentials used > > > > > > > + * @targ_ns: The user namespace of the resource being accessed > > > > > > > + * @capable_ns: The user namespace in which the credential provides the > > > > > > > + * capability to access the targeted resource. > > > > > > > + * This will be NULL if ret is not 0. > > > > > > > + * @cap: The capability to check for > > > > > > > + * @opts: Bitmask of options defined in include/linux/security.h > > > > > > > + * @ret: The return value of the check: 0 if it does, -ve if it does not > > > > > > > + * > > > > > > > + * Allows to trace calls to cap_capable in commoncap.c > > > > > > > + */ > > > > > > > +TRACE_EVENT(cap_capable, > > > > > > > + > > > > > > > + TP_PROTO(const struct cred *cred, struct user_namespace *targ_ns, > > > > > > > + struct user_namespace *capable_ns, int cap, unsigned int opts, int ret), > > > > > > > + > > > > > > > + TP_ARGS(cred, targ_ns, capable_ns, cap, opts, ret), > > > > > > > + > > > > > > > + TP_STRUCT__entry( > > > > > > > + __field(const struct cred *, cred) > > > > > > > + __field(struct user_namespace *, targ_ns) > > > > > > > + __field(struct user_namespace *, capable_ns) > > > > > > > + __field(int, cap) > > > > > > > + __field(unsigned int, opts) > > > > > > > + __field(int, ret) > > > > > > > + ), > > > > > > > + > > > > > > > + TP_fast_assign( > > > > > > > + __entry->cred = cred; > > > > > > > + __entry->targ_ns = targ_ns; > > > > > > > + __entry->capable_ns = capable_ns; > > > > > > > + __entry->cap = cap; > > > > > > > + __entry->opts = opts; > > > > > > > + __entry->ret = ret; > > > > > > > + ), > > > > > > > + > > > > > > > + TP_printk("cred %p, targ_ns %p, capable_ns %p, cap %d, opts %u, ret %d", > > > > > > > + __entry->cred, __entry->targ_ns, __entry->capable_ns, __entry->cap, > > > > > > > + __entry->opts, __entry->ret) > > > > > > > +); > > > > > > > + > > > > > > > +#endif /* _TRACE_CAPABILITY_H */ > > > > > > > + > > > > > > > +/* This part must be outside protection */ > > > > > > > +#include <trace/define_trace.h> > > > > > > > diff --git a/security/commoncap.c b/security/commoncap.c > > > > > > > index 162d96b3a676..12c3ddfe0d6e 100644 > > > > > > > --- a/security/commoncap.c > > > > > > > +++ b/security/commoncap.c > > > > > > > @@ -27,6 +27,9 @@ > > > > > > > #include <linux/mnt_idmapping.h> > > > > > > > #include <uapi/linux/lsm.h> > > > > > > > > > > > > > > +#define CREATE_TRACE_POINTS > > > > > > > +#include <trace/events/capability.h> > > > > > > > + > > > > > > > /* > > > > > > > * If a non-root user executes a setuid-root binary in > > > > > > > * !secure(SECURE_NOROOT) mode, then we raise capabilities. > > > > > > > @@ -52,7 +55,7 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) > > > > > > > /** > > > > > > > * cap_capable - Determine whether a task has a particular effective capability > > > > > > > * @cred: The credentials to use > > > > > > > - * @targ_ns: The user namespace in which we need the capability > > > > > > > + * @targ_ns: The user namespace of the resource being accessed > > > > > > > * @cap: The capability to check for > > > > > > > * @opts: Bitmask of options defined in include/linux/security.h > > > > > > > * > > > > > > > @@ -68,6 +71,7 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > > > > > int cap, unsigned int opts) > > > > > > > { > > > > > > > struct user_namespace *ns = targ_ns; > > > > > > > + int ret = -EPERM; > > > > > > > > > > > > > > /* See if cred has the capability in the target user namespace > > > > > > > * by examining the target user namespace and all of the target > > > > > > > @@ -75,22 +79,32 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > > > > > */ > > > > > > > for (;;) { > > > > > > > /* Do we have the necessary capabilities? */ > > > > > > > - if (ns == cred->user_ns) > > > > > > > - return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; > > > > > > > + if (ns == cred->user_ns) { > > > > > > > + if (cap_raised(cred->cap_effective, cap)) > > > > > > > + ret = 0; > > > > > > > + else > > > > > > > + ns = NULL; > > > > > > > > > > > > This is a bit unfortunate :( so maybe all we needed was `ns = > > > > > > ns->parent` for that one use case, and keep the original `ret ? NULL : > > > > > > ns` inside trace_cap_capable(). > > > > > > > > > > Yeah, that would be fine with me. Or maybe just doing > > > > > > > > > > /* in case of an error, trace should show ns=NULL */ > > > > > if (ret) > > > > > ns = NULL; > > > > > > > > > > right above the trace_cap_capable() call would be clearer. > > > > > > > > I feel like having less trace specific logic in this function would be > > > > a good thing, > > > > so I'm for Andrii's suggestion of doing the ret check there but also > > > > fine to do what security folks prefer :) > > > > > > I think a comment is needed to remind us (me) in 2 years why the > > > seting of ns to NULL is there. But the comment of trace_cap_capable() > > > probably suffices, so sure, go with Andrii's suggestion. And then > > > > > > Reviewed-by: Serge Hallyn <serge@hallyn.com> > > > > > > for the capability code. > > > > > > thanks, > > > -serge > > > > I think we're suggesting to not set ns = NULL here and instead > > check the ret value in the trace code e.g. > > `__entry->capable_ns = ret ? NULL : capable_ns;` > > Perfect. Was originally going to suggest this, but then thought well > the rest of the ns logic is purely capability not tracing related. > But since the comment is in trace_cap_capable(), putting the assignment > there makes sense. > Actually, I had another idea. What about just having a separate variable in the `cap_capable` function for `capable_ns` that only gets set if ret is 0. Then we're not changing the `ns` variable at all for the purposes of the trace function. > > I think the only trace-specific thing, which I can add a comment > > for, is this part `ns = ns->parent;` after we already set the ret to 0.
On Sun, Oct 27, 2024 at 02:21:26PM -0400, Jordan Rome wrote: > On Sat, Oct 26, 2024 at 9:00 AM Serge E. Hallyn <serge@hallyn.com> wrote: > > > > On Sat, Oct 26, 2024 at 07:22:29AM -0400, Jordan Rome wrote: > > > On Sat, Oct 26, 2024 at 6:10 AM Serge E. Hallyn <serge@hallyn.com> wrote: > > > > > > > > On Fri, Oct 25, 2024 at 04:24:05PM -0400, Jordan Rome wrote: > > > > > On Fri, Oct 25, 2024 at 3:52 PM Serge E. Hallyn <serge@hallyn.com> wrote: > > > > > > > > > > > > On Fri, Oct 25, 2024 at 11:37:59AM -0700, Andrii Nakryiko wrote: > > > > > > > On Fri, Oct 25, 2024 at 8:15 AM Jordan Rome <linux@jordanrome.com> wrote: > > > > > > > > > > > > > > > > In cases where we want a stable way to observe/trace > > > > > > > > cap_capable (e.g. protection from inlining and API updates) > > > > > > > > add a tracepoint that passes: > > > > > > > > - The credentials used > > > > > > > > - The user namespace of the resource being accessed > > > > > > > > - The user namespace that has the capability to access the > > > > > > > > targeted resource > > > > > > > > - The capability to check for > > > > > > > > - Bitmask of options defined in include/linux/security.h > > > > > > > > - The return value of the check > > > > > > > > > > > > > > > > Signed-off-by: Jordan Rome <linux@jordanrome.com> > > > > > > > > --- > > > > > > > > MAINTAINERS | 1 + > > > > > > > > include/trace/events/capability.h | 60 +++++++++++++++++++++++++++++++ > > > > > > > > security/commoncap.c | 31 +++++++++++----- > > > > > > > > 3 files changed, 84 insertions(+), 8 deletions(-) > > > > > > > > create mode 100644 include/trace/events/capability.h > > > > > > > > > > > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > > > > > > index cc40a9d9b8cd..210e9076c858 100644 > > > > > > > > --- a/MAINTAINERS > > > > > > > > +++ b/MAINTAINERS > > > > > > > > @@ -4994,6 +4994,7 @@ M: Serge Hallyn <serge@hallyn.com> > > > > > > > > L: linux-security-module@vger.kernel.org > > > > > > > > S: Supported > > > > > > > > F: include/linux/capability.h > > > > > > > > +F: include/trace/events/capability.h > > > > > > > > F: include/uapi/linux/capability.h > > > > > > > > F: kernel/capability.c > > > > > > > > F: security/commoncap.c > > > > > > > > diff --git a/include/trace/events/capability.h b/include/trace/events/capability.h > > > > > > > > new file mode 100644 > > > > > > > > index 000000000000..e706ce690c38 > > > > > > > > --- /dev/null > > > > > > > > +++ b/include/trace/events/capability.h > > > > > > > > @@ -0,0 +1,60 @@ > > > > > > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > > > > > > +#undef TRACE_SYSTEM > > > > > > > > +#define TRACE_SYSTEM capability > > > > > > > > + > > > > > > > > +#if !defined(_TRACE_CAPABILITY_H) || defined(TRACE_HEADER_MULTI_READ) > > > > > > > > +#define _TRACE_CAPABILITY_H > > > > > > > > + > > > > > > > > +#include <linux/cred.h> > > > > > > > > +#include <linux/tracepoint.h> > > > > > > > > +#include <linux/user_namespace.h> > > > > > > > > + > > > > > > > > +/** > > > > > > > > + * cap_capable - called after it's determined if a task has a particular > > > > > > > > + * effective capability > > > > > > > > + * > > > > > > > > + * @cred: The credentials used > > > > > > > > + * @targ_ns: The user namespace of the resource being accessed > > > > > > > > + * @capable_ns: The user namespace in which the credential provides the > > > > > > > > + * capability to access the targeted resource. > > > > > > > > + * This will be NULL if ret is not 0. > > > > > > > > + * @cap: The capability to check for > > > > > > > > + * @opts: Bitmask of options defined in include/linux/security.h > > > > > > > > + * @ret: The return value of the check: 0 if it does, -ve if it does not > > > > > > > > + * > > > > > > > > + * Allows to trace calls to cap_capable in commoncap.c > > > > > > > > + */ > > > > > > > > +TRACE_EVENT(cap_capable, > > > > > > > > + > > > > > > > > + TP_PROTO(const struct cred *cred, struct user_namespace *targ_ns, > > > > > > > > + struct user_namespace *capable_ns, int cap, unsigned int opts, int ret), > > > > > > > > + > > > > > > > > + TP_ARGS(cred, targ_ns, capable_ns, cap, opts, ret), > > > > > > > > + > > > > > > > > + TP_STRUCT__entry( > > > > > > > > + __field(const struct cred *, cred) > > > > > > > > + __field(struct user_namespace *, targ_ns) > > > > > > > > + __field(struct user_namespace *, capable_ns) > > > > > > > > + __field(int, cap) > > > > > > > > + __field(unsigned int, opts) > > > > > > > > + __field(int, ret) > > > > > > > > + ), > > > > > > > > + > > > > > > > > + TP_fast_assign( > > > > > > > > + __entry->cred = cred; > > > > > > > > + __entry->targ_ns = targ_ns; > > > > > > > > + __entry->capable_ns = capable_ns; > > > > > > > > + __entry->cap = cap; > > > > > > > > + __entry->opts = opts; > > > > > > > > + __entry->ret = ret; > > > > > > > > + ), > > > > > > > > + > > > > > > > > + TP_printk("cred %p, targ_ns %p, capable_ns %p, cap %d, opts %u, ret %d", > > > > > > > > + __entry->cred, __entry->targ_ns, __entry->capable_ns, __entry->cap, > > > > > > > > + __entry->opts, __entry->ret) > > > > > > > > +); > > > > > > > > + > > > > > > > > +#endif /* _TRACE_CAPABILITY_H */ > > > > > > > > + > > > > > > > > +/* This part must be outside protection */ > > > > > > > > +#include <trace/define_trace.h> > > > > > > > > diff --git a/security/commoncap.c b/security/commoncap.c > > > > > > > > index 162d96b3a676..12c3ddfe0d6e 100644 > > > > > > > > --- a/security/commoncap.c > > > > > > > > +++ b/security/commoncap.c > > > > > > > > @@ -27,6 +27,9 @@ > > > > > > > > #include <linux/mnt_idmapping.h> > > > > > > > > #include <uapi/linux/lsm.h> > > > > > > > > > > > > > > > > +#define CREATE_TRACE_POINTS > > > > > > > > +#include <trace/events/capability.h> > > > > > > > > + > > > > > > > > /* > > > > > > > > * If a non-root user executes a setuid-root binary in > > > > > > > > * !secure(SECURE_NOROOT) mode, then we raise capabilities. > > > > > > > > @@ -52,7 +55,7 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) > > > > > > > > /** > > > > > > > > * cap_capable - Determine whether a task has a particular effective capability > > > > > > > > * @cred: The credentials to use > > > > > > > > - * @targ_ns: The user namespace in which we need the capability > > > > > > > > + * @targ_ns: The user namespace of the resource being accessed > > > > > > > > * @cap: The capability to check for > > > > > > > > * @opts: Bitmask of options defined in include/linux/security.h > > > > > > > > * > > > > > > > > @@ -68,6 +71,7 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > > > > > > int cap, unsigned int opts) > > > > > > > > { > > > > > > > > struct user_namespace *ns = targ_ns; > > > > > > > > + int ret = -EPERM; > > > > > > > > > > > > > > > > /* See if cred has the capability in the target user namespace > > > > > > > > * by examining the target user namespace and all of the target > > > > > > > > @@ -75,22 +79,32 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > > > > > > > > */ > > > > > > > > for (;;) { > > > > > > > > /* Do we have the necessary capabilities? */ > > > > > > > > - if (ns == cred->user_ns) > > > > > > > > - return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; > > > > > > > > + if (ns == cred->user_ns) { > > > > > > > > + if (cap_raised(cred->cap_effective, cap)) > > > > > > > > + ret = 0; > > > > > > > > + else > > > > > > > > + ns = NULL; > > > > > > > > > > > > > > This is a bit unfortunate :( so maybe all we needed was `ns = > > > > > > > ns->parent` for that one use case, and keep the original `ret ? NULL : > > > > > > > ns` inside trace_cap_capable(). > > > > > > > > > > > > Yeah, that would be fine with me. Or maybe just doing > > > > > > > > > > > > /* in case of an error, trace should show ns=NULL */ > > > > > > if (ret) > > > > > > ns = NULL; > > > > > > > > > > > > right above the trace_cap_capable() call would be clearer. > > > > > > > > > > I feel like having less trace specific logic in this function would be > > > > > a good thing, > > > > > so I'm for Andrii's suggestion of doing the ret check there but also > > > > > fine to do what security folks prefer :) > > > > > > > > I think a comment is needed to remind us (me) in 2 years why the > > > > seting of ns to NULL is there. But the comment of trace_cap_capable() > > > > probably suffices, so sure, go with Andrii's suggestion. And then > > > > > > > > Reviewed-by: Serge Hallyn <serge@hallyn.com> > > > > > > > > for the capability code. > > > > > > > > thanks, > > > > -serge > > > > > > I think we're suggesting to not set ns = NULL here and instead > > > check the ret value in the trace code e.g. > > > `__entry->capable_ns = ret ? NULL : capable_ns;` > > > > Perfect. Was originally going to suggest this, but then thought well > > the rest of the ns logic is purely capability not tracing related. > > But since the comment is in trace_cap_capable(), putting the assignment > > there makes sense. > > > > Actually, I had another idea. What about just having a separate > variable in the `cap_capable` function for `capable_ns` that only gets > set if ret is 0. Then we're not changing the `ns` variable at all for > the purposes of the trace function. FWIW that sounds great. -serge
diff --git a/MAINTAINERS b/MAINTAINERS index cc40a9d9b8cd..210e9076c858 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4994,6 +4994,7 @@ M: Serge Hallyn <serge@hallyn.com> L: linux-security-module@vger.kernel.org S: Supported F: include/linux/capability.h +F: include/trace/events/capability.h F: include/uapi/linux/capability.h F: kernel/capability.c F: security/commoncap.c diff --git a/include/trace/events/capability.h b/include/trace/events/capability.h new file mode 100644 index 000000000000..e706ce690c38 --- /dev/null +++ b/include/trace/events/capability.h @@ -0,0 +1,60 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM capability + +#if !defined(_TRACE_CAPABILITY_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_CAPABILITY_H + +#include <linux/cred.h> +#include <linux/tracepoint.h> +#include <linux/user_namespace.h> + +/** + * cap_capable - called after it's determined if a task has a particular + * effective capability + * + * @cred: The credentials used + * @targ_ns: The user namespace of the resource being accessed + * @capable_ns: The user namespace in which the credential provides the + * capability to access the targeted resource. + * This will be NULL if ret is not 0. + * @cap: The capability to check for + * @opts: Bitmask of options defined in include/linux/security.h + * @ret: The return value of the check: 0 if it does, -ve if it does not + * + * Allows to trace calls to cap_capable in commoncap.c + */ +TRACE_EVENT(cap_capable, + + TP_PROTO(const struct cred *cred, struct user_namespace *targ_ns, + struct user_namespace *capable_ns, int cap, unsigned int opts, int ret), + + TP_ARGS(cred, targ_ns, capable_ns, cap, opts, ret), + + TP_STRUCT__entry( + __field(const struct cred *, cred) + __field(struct user_namespace *, targ_ns) + __field(struct user_namespace *, capable_ns) + __field(int, cap) + __field(unsigned int, opts) + __field(int, ret) + ), + + TP_fast_assign( + __entry->cred = cred; + __entry->targ_ns = targ_ns; + __entry->capable_ns = capable_ns; + __entry->cap = cap; + __entry->opts = opts; + __entry->ret = ret; + ), + + TP_printk("cred %p, targ_ns %p, capable_ns %p, cap %d, opts %u, ret %d", + __entry->cred, __entry->targ_ns, __entry->capable_ns, __entry->cap, + __entry->opts, __entry->ret) +); + +#endif /* _TRACE_CAPABILITY_H */ + +/* This part must be outside protection */ +#include <trace/define_trace.h> diff --git a/security/commoncap.c b/security/commoncap.c index 162d96b3a676..12c3ddfe0d6e 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -27,6 +27,9 @@ #include <linux/mnt_idmapping.h> #include <uapi/linux/lsm.h> +#define CREATE_TRACE_POINTS +#include <trace/events/capability.h> + /* * If a non-root user executes a setuid-root binary in * !secure(SECURE_NOROOT) mode, then we raise capabilities. @@ -52,7 +55,7 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) /** * cap_capable - Determine whether a task has a particular effective capability * @cred: The credentials to use - * @targ_ns: The user namespace in which we need the capability + * @targ_ns: The user namespace of the resource being accessed * @cap: The capability to check for * @opts: Bitmask of options defined in include/linux/security.h * @@ -68,6 +71,7 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, int cap, unsigned int opts) { struct user_namespace *ns = targ_ns; + int ret = -EPERM; /* See if cred has the capability in the target user namespace * by examining the target user namespace and all of the target @@ -75,22 +79,32 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, */ for (;;) { /* Do we have the necessary capabilities? */ - if (ns == cred->user_ns) - return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; + if (ns == cred->user_ns) { + if (cap_raised(cred->cap_effective, cap)) + ret = 0; + else + ns = NULL; + break; + } /* * If we're already at a lower level than we're looking for, * we're done searching. */ - if (ns->level <= cred->user_ns->level) - return -EPERM; + if (ns->level <= cred->user_ns->level) { + ns = NULL; + break; + } /* * The owner of the user namespace in the parent of the * user namespace has all caps. */ - if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) - return 0; + if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) { + ns = ns->parent; + ret = 0; + break; + } /* * If you have a capability in a parent user ns, then you have @@ -99,7 +113,8 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, ns = ns->parent; } - /* We never get here */ + trace_cap_capable(cred, targ_ns, ns, cap, opts, ret); + return ret; } /**
In cases where we want a stable way to observe/trace cap_capable (e.g. protection from inlining and API updates) add a tracepoint that passes: - The credentials used - The user namespace of the resource being accessed - The user namespace that has the capability to access the targeted resource - The capability to check for - Bitmask of options defined in include/linux/security.h - The return value of the check Signed-off-by: Jordan Rome <linux@jordanrome.com> --- MAINTAINERS | 1 + include/trace/events/capability.h | 60 +++++++++++++++++++++++++++++++ security/commoncap.c | 31 +++++++++++----- 3 files changed, 84 insertions(+), 8 deletions(-) create mode 100644 include/trace/events/capability.h -- 2.43.5