Question on commit dc7109aaa233 ("futex: Validate waiter correctly in futex_proxy_trylock_atomic()")

[Lukas Bulwahn]

Dear Thomas,

in commit dc7109aaa233 ("futex: Validate waiter correctly in
futex_proxy_trylock_atomic()") visible on next-20210819, you add:

+    /*
+     * Ensure that this is a waiter sitting in futex_wait_requeue_pi()
+     * and waiting on the 'waitqueue' futex which is always !PI.
+     */
+    if (!top_waiter->rt_waiter || top_waiter->pi_state)
+        ret = -EINVAL;

However, ret is unconditionally reassigned later and erases any
intended effect of this assignment. This is making that assignment
above a Dead Store, which clang-analyzer correctly warns about and
which motivates me to write you an email.

Did you intend to return -EINVAL here? So:

+       if (!top_waiter->rt_waiter || top_waiter->pi_state)
+               return -EINVAL;



Best regards,

Lukas

Static analysis tools are as foolish as they are... but every dog has its day...