On 8/17/20 1:07 PM, Thiébaud Weksteen wrote:
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 <tw...@google.com> Suggested-by: Joel Fernandes <joe...@google.com> Reviewed-by: Peter Enderborg <peter.enderb...@sony.com>
Acked-by: Stephen Smalley <stephen.smalley.w...@gmail.com>
