Smack: Handle io_uring kernel thread privileges

Smack assumes that kernel threads are privileged for smackfs
operations. This was necessary because the credential of the
kernel thread was not related to a user operation. With io_uring
the credential does reflect a user's rights and can be used.

Suggested-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index efe2406..7eabb44 100644 (file)
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -688,9 +688,10 @@ bool smack_privileged_cred(int cap, const struct cred *cred)
 bool smack_privileged(int cap)
 {
        /*
-        * All kernel tasks are privileged
+        * Kernel threads may not have credentials we can use.
+        * The io_uring kernel threads do have reliable credentials.
         */
-       if (unlikely(current->flags & PF_KTHREAD))
+       if ((current->flags & (PF_KTHREAD | PF_IO_WORKER)) == PF_KTHREAD)
                return true;
 
        return smack_privileged_cred(cap, current_cred());