ptrace: do not audit capability check when outputing /proc/pid/stat

Reading /proc/pid/stat of another process checks if one has ptrace permissions
on that process.  If one does have permissions it outputs some data about the
process which might have security and attack implications.  If the current
task does not have ptrace permissions the read still works, but those fields
are filled with inocuous (0) values.  Since this check and a subsequent denial
is not a violation of the security policy we should not audit such denials.

This can be quite useful to removing ptrace broadly across a system without
flooding the logs when ps is run or something which harmlessly walks proc.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index c9605c4a2e08..14f94cd29c80 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1809,7 +1809,7 @@ static int selinux_ptrace_access_check(struct task_struct *child,
         if (rc)
                 return rc;
 
-        if (mode == PTRACE_MODE_READ) {
+        if (mode & PTRACE_MODE_READ) {
                 u32 sid = current_sid();
                 u32 csid = task_sid(child);
                 return avc_has_perm(sid, csid, SECCLASS_FILE, FILE__READ, NULL);