selinux: avoid silent denials in permissive mode under RCU walk
commit 0dc1ba24f7fff6 ("SELINUX: Make selinux cache VFS RCU walks safe")
results in no audit messages at all if in permissive mode because the
cache is updated during the rcu walk and thus no denial occurs on
the subsequent ref walk. Fix this by not updating the cache when
performing a non-blocking permission check. This only affects search
and symlink read checks during rcu walk.
Fixes: 0dc1ba24f7fff6 ("SELINUX: Make selinux cache VFS RCU walks safe")
Reported-by: BMK <bmktuwien@gmail.com>
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index f0e36c3..7f60684 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2982,7 +2982,9 @@ static int selinux_inode_permission(struct inode *inode, int mask)
return PTR_ERR(isec);
rc = avc_has_perm_noaudit(&selinux_state,
- sid, isec->sid, isec->sclass, perms, 0, &avd);
+ sid, isec->sid, isec->sclass, perms,
+ (flags & MAY_NOT_BLOCK) ? AVC_NONBLOCKING : 0,
+ &avd);
audited = avc_audit_required(perms, &avd, rc,
from_access ? FILE__AUDIT_ACCESS : 0,
&denied);