diff options
| author | Thiébaud Weksteen <tweek@google.com> | 2020-08-21 16:08:21 +0200 |
|---|---|---|
| committer | Paul Moore <paul@paul-moore.com> | 2020-08-21 17:05:22 -0400 |
| commit | dd8166212d9a2eca3181567c953d5687aea4d7dc (patch) | |
| tree | 8e5bbcd78580c50a5bd50e238073a7ad655eb040 | |
| parent | 0eea6091539b15572cd278b8d62893c058bdb292 (diff) | |
selinux: add tracepoint on audited events
The audit data currently captures which process and which target
is responsible for a denial. There is no data on where exactly in the
process that call occurred. Debugging can be made easier by being able to
reconstruct the unified kernel and userland stack traces [1]. Add a
tracepoint on the SELinux denials which can then be used by userland
(i.e. perf).
Although this patch could manually be added by each OS developer to
trouble shoot a denial, adding it to the kernel streamlines the
developers workflow.
It is possible to use perf for monitoring the event:
# perf record -e avc:selinux_audited -g -a
^C
# perf report -g
[...]
6.40% 6.40% audited=800000 tclass=4
|
__libc_start_main
|
|--4.60%--__GI___ioctl
| entry_SYSCALL_64
| do_syscall_64
| __x64_sys_ioctl
| ksys_ioctl
| binder_ioctl
| binder_set_nice
| can_nice
| capable
| security_capable
| cred_has_capability.isra.0
| slow_avc_audit
| common_lsm_audit
| avc_audit_post_callback
| avc_audit_post_callback
|
It is also possible to use the ftrace interface:
# echo 1 > /sys/kernel/debug/tracing/events/avc/selinux_audited/enable
# cat /sys/kernel/debug/tracing/trace
tracer: nop
entries-in-buffer/entries-written: 1/1 #P:8
[...]
dmesg-3624 [001] 13072.325358: selinux_denied: audited=800000 tclass=4
The tclass value can be mapped to a class by searching
security/selinux/flask.h. The audited value is a bit field of the
permissions described in security/selinux/av_permissions.h for the
corresponding class.
[1] https://source.android.com/devices/tech/debug/native_stack_dump
Signed-off-by: Thiébaud Weksteen <tweek@google.com>
Suggested-by: Joel Fernandes <joelaf@google.com>
Reviewed-by: Peter Enderborg <peter.enderborg@sony.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
| -rw-r--r-- | MAINTAINERS | 1 | ||||
| -rw-r--r-- | include/trace/events/avc.h | 37 | ||||
| -rw-r--r-- | security/selinux/avc.c | 5 |
3 files changed, 43 insertions, 0 deletions
diff --git a/MAINTAINERS b/MAINTAINERS index deaafb617361..ed19f56503f4 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -15569,6 +15569,7 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux.git F: Documentation/ABI/obsolete/sysfs-selinux-checkreqprot F: Documentation/ABI/obsolete/sysfs-selinux-disable F: Documentation/admin-guide/LSM/SELinux.rst +F: include/trace/events/avc.h F: include/uapi/linux/selinux_netlink.h F: scripts/selinux/ F: security/selinux/ diff --git a/include/trace/events/avc.h b/include/trace/events/avc.h new file mode 100644 index 000000000000..07c058a9bbcd --- /dev/null +++ b/include/trace/events/avc.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Author: Thiébaud Weksteen <tweek@google.com> + */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM avc + +#if !defined(_TRACE_SELINUX_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_SELINUX_H + +#include <linux/tracepoint.h> + +TRACE_EVENT(selinux_audited, + + TP_PROTO(struct selinux_audit_data *sad), + + TP_ARGS(sad), + + TP_STRUCT__entry( + __field(unsigned int, tclass) + __field(unsigned int, audited) + ), + + TP_fast_assign( + __entry->tclass = sad->tclass; + __entry->audited = sad->audited; + ), + + TP_printk("tclass=%u audited=%x", + __entry->tclass, + __entry->audited) +); + +#endif + +/* This part must be outside protection */ +#include <trace/define_trace.h> diff --git a/security/selinux/avc.c b/security/selinux/avc.c index d18cb32a242a..b0a0af778b70 100644 --- a/security/selinux/avc.c +++ b/security/selinux/avc.c @@ -31,6 +31,9 @@ #include "avc_ss.h" #include "classmap.h" +#define CREATE_TRACE_POINTS +#include <trace/events/avc.h> + #define AVC_CACHE_SLOTS 512 #define AVC_DEF_CACHE_THRESHOLD 512 #define AVC_CACHE_RECLAIM 16 @@ -706,6 +709,8 @@ static void avc_audit_post_callback(struct audit_buffer *ab, void *a) u32 scontext_len; int rc; + trace_selinux_audited(sad); + rc = security_sid_to_context(sad->state, sad->ssid, &scontext, &scontext_len); if (rc) |