linux-kernel - Re: [PATCH][next] futex: fix assigned ret variable that is never read

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Date:   Wed, 1 Sep 2021 13:24:25 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Colin King <colin.king@...onical.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Darren Hart <dvhart@...radead.org>,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] futex: fix assigned ret variable that is never read

On Wed, 18 Aug 2021, Colin King wrote:

>From: Colin Ian King <colin.king@...onical.com>
>
>Currently the check on the rt_waiter and top_waiter->pi_state is
>assigning an error return code to ret but this later gets re-assigned,
>hence the check is currently ineffective. I believe the original
>intent was to return -EINVAL rather than assign it to ret. Fix this.

LGTM.

Acked-by: Davidlohr Bueso <dbueso@...e.de>

>
>Addresses-Coverity: ("Unused value")
>Fixes: dc7109aaa233 ("futex: Validate waiter correctly in futex_proxy_trylock_atomic()")
>Signed-off-by: Colin Ian King <colin.king@...onical.com>
>---
> kernel/futex.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/kernel/futex.c b/kernel/futex.c
>index e7b4c6121da4..30e7daebaec8 100644
>--- a/kernel/futex.c
>+++ b/kernel/futex.c
>@@ -2025,7 +2025,7 @@ futex_proxy_trylock_atomic(u32 __user *pifutex, struct futex_hash_bucket *hb1,
>	 * and waiting on the 'waitqueue' futex which is always !PI.
>	 */
>	if (!top_waiter->rt_waiter || top_waiter->pi_state)
>-		ret = -EINVAL;
>+		return -EINVAL;
>
>	/* Ensure we requeue to the expected futex. */
>	if (!match_futex(top_waiter->requeue_pi_key, key2))
>--
>2.32.0
>