| Message ID | 20241204155911.1817092-1-linux@jordanrome.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v9] security: add trace event for cap_capable | expand |
On Wed, Dec 04, 2024 at 07:59:11AM -0800, Jordan Rome 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 in which the credential provides the > capability to access the targeted resource > - The capability to check for > - The return value of the check > > Signed-off-by: Jordan Rome <linux@jordanrome.com> Thanks, applied to caps-next. > --- > MAINTAINERS | 1 + > include/trace/events/capability.h | 57 +++++++++++++++++++++++++++++++ > security/commoncap.c | 54 ++++++++++++++++++++++------- > 3 files changed, 99 insertions(+), 13 deletions(-) > create mode 100644 include/trace/events/capability.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index 1e930c7a58b1..33fde7f660d0 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -5147,6 +5147,7 @@ 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..17340257946c > --- /dev/null > +++ b/include/trace/events/capability.h > @@ -0,0 +1,57 @@ > +/* 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 > + * @target_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 > + * @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 *target_ns, > + const struct user_namespace *capable_ns, int cap, int ret), > + > + TP_ARGS(cred, target_ns, capable_ns, cap, ret), > + > + TP_STRUCT__entry( > + __field(const struct cred *, cred) > + __field(struct user_namespace *, target_ns) > + __field(const struct user_namespace *, capable_ns) > + __field(int, cap) > + __field(int, ret) > + ), > + > + TP_fast_assign( > + __entry->cred = cred; > + __entry->target_ns = target_ns; > + __entry->capable_ns = ret == 0 ? capable_ns : NULL; > + __entry->cap = cap; > + __entry->ret = ret; > + ), > + > + TP_printk("cred %p, target_ns %p, capable_ns %p, cap %d, ret %d", > + __entry->cred, __entry->target_ns, __entry->capable_ns, __entry->cap, > + __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 cefad323a0b1..7b6984b27127 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. > @@ -50,24 +53,24 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) > } > > /** > - * cap_capable - Determine whether a task has a particular effective capability > + * cap_capable_helper - 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 > + * @target_ns: The user namespace of the resource being accessed > + * @cred_ns: The user namespace of the credentials > * @cap: The capability to check for > - * @opts: Bitmask of options defined in include/linux/security.h > * > * Determine whether the nominated task has the specified capability amongst > * its effective set, returning 0 if it does, -ve if it does not. > * > - * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() > - * and has_capability() functions. That is, it has the reverse semantics: > - * cap_has_capability() returns 0 when a task has a capability, but the > - * kernel's capable() and has_capability() returns 1 for this case. > + * See cap_capable for more details. > */ > -int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > - int cap, unsigned int opts) > +static inline int cap_capable_helper(const struct cred *cred, > + struct user_namespace *target_ns, > + const struct user_namespace *cred_ns, > + int cap) > { > - struct user_namespace *ns = targ_ns; > + struct user_namespace *ns = target_ns; > > /* See if cred has the capability in the target user namespace > * by examining the target user namespace and all of the target > @@ -75,21 +78,21 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > */ > for (;;) { > /* Do we have the necessary capabilities? */ > - if (ns == cred->user_ns) > + if (likely(ns == cred_ns)) > return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; > > /* > * If we're already at a lower level than we're looking for, > * we're done searching. > */ > - if (ns->level <= cred->user_ns->level) > + if (ns->level <= cred_ns->level) > return -EPERM; > > /* > * 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)) > + if ((ns->parent == cred_ns) && uid_eq(ns->owner, cred->euid)) > return 0; > > /* > @@ -102,6 +105,31 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > /* We never get here */ > } > > +/** > + * cap_capable - Determine whether a task has a particular effective capability > + * @cred: The credentials to use > + * @target_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 (unused) > + * > + * Determine whether the nominated task has the specified capability amongst > + * its effective set, returning 0 if it does, -ve if it does not. > + * > + * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() > + * and has_capability() functions. That is, it has the reverse semantics: > + * cap_has_capability() returns 0 when a task has a capability, but the > + * kernel's capable() and has_capability() returns 1 for this case. > + */ > +int cap_capable(const struct cred *cred, struct user_namespace *target_ns, > + int cap, unsigned int opts) > +{ > + const struct user_namespace *cred_ns = cred->user_ns; > + int ret = cap_capable_helper(cred, target_ns, cred_ns, cap); > + > + trace_cap_capable(cred, target_ns, cred_ns, cap, ret); > + return ret; > +} > + > /** > * cap_settime - Determine whether the current process may set the system clock > * @ts: The time to set > -- > 2.43.5
diff --git a/MAINTAINERS b/MAINTAINERS index 1e930c7a58b1..33fde7f660d0 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5147,6 +5147,7 @@ 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..17340257946c --- /dev/null +++ b/include/trace/events/capability.h @@ -0,0 +1,57 @@ +/* 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 + * @target_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 + * @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 *target_ns, + const struct user_namespace *capable_ns, int cap, int ret), + + TP_ARGS(cred, target_ns, capable_ns, cap, ret), + + TP_STRUCT__entry( + __field(const struct cred *, cred) + __field(struct user_namespace *, target_ns) + __field(const struct user_namespace *, capable_ns) + __field(int, cap) + __field(int, ret) + ), + + TP_fast_assign( + __entry->cred = cred; + __entry->target_ns = target_ns; + __entry->capable_ns = ret == 0 ? capable_ns : NULL; + __entry->cap = cap; + __entry->ret = ret; + ), + + TP_printk("cred %p, target_ns %p, capable_ns %p, cap %d, ret %d", + __entry->cred, __entry->target_ns, __entry->capable_ns, __entry->cap, + __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 cefad323a0b1..7b6984b27127 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. @@ -50,24 +53,24 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) } /** - * cap_capable - Determine whether a task has a particular effective capability + * cap_capable_helper - 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 + * @target_ns: The user namespace of the resource being accessed + * @cred_ns: The user namespace of the credentials * @cap: The capability to check for - * @opts: Bitmask of options defined in include/linux/security.h * * Determine whether the nominated task has the specified capability amongst * its effective set, returning 0 if it does, -ve if it does not. * - * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() - * and has_capability() functions. That is, it has the reverse semantics: - * cap_has_capability() returns 0 when a task has a capability, but the - * kernel's capable() and has_capability() returns 1 for this case. + * See cap_capable for more details. */ -int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, - int cap, unsigned int opts) +static inline int cap_capable_helper(const struct cred *cred, + struct user_namespace *target_ns, + const struct user_namespace *cred_ns, + int cap) { - struct user_namespace *ns = targ_ns; + struct user_namespace *ns = target_ns; /* See if cred has the capability in the target user namespace * by examining the target user namespace and all of the target @@ -75,21 +78,21 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, */ for (;;) { /* Do we have the necessary capabilities? */ - if (ns == cred->user_ns) + if (likely(ns == cred_ns)) return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; /* * If we're already at a lower level than we're looking for, * we're done searching. */ - if (ns->level <= cred->user_ns->level) + if (ns->level <= cred_ns->level) return -EPERM; /* * 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)) + if ((ns->parent == cred_ns) && uid_eq(ns->owner, cred->euid)) return 0; /* @@ -102,6 +105,31 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, /* We never get here */ } +/** + * cap_capable - Determine whether a task has a particular effective capability + * @cred: The credentials to use + * @target_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 (unused) + * + * Determine whether the nominated task has the specified capability amongst + * its effective set, returning 0 if it does, -ve if it does not. + * + * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() + * and has_capability() functions. That is, it has the reverse semantics: + * cap_has_capability() returns 0 when a task has a capability, but the + * kernel's capable() and has_capability() returns 1 for this case. + */ +int cap_capable(const struct cred *cred, struct user_namespace *target_ns, + int cap, unsigned int opts) +{ + const struct user_namespace *cred_ns = cred->user_ns; + int ret = cap_capable_helper(cred, target_ns, cred_ns, cap); + + trace_cap_capable(cred, target_ns, cred_ns, cap, ret); + return ret; +} + /** * cap_settime - Determine whether the current process may set the system clock * @ts: The time to set
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 in which the credential provides the capability to access the targeted resource - The capability to check for - The return value of the check Signed-off-by: Jordan Rome <linux@jordanrome.com> --- MAINTAINERS | 1 + include/trace/events/capability.h | 57 +++++++++++++++++++++++++++++++ security/commoncap.c | 54 ++++++++++++++++++++++------- 3 files changed, 99 insertions(+), 13 deletions(-) create mode 100644 include/trace/events/capability.h -- 2.43.5