@@ -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
new file mode 100644
@@ -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>
@@ -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