From: sashiko-bot@kernel.org
Cc: linux-security-module@vger.kernel.org
Subject: Re: [PATCH v2] cred: annotate data race on non_rcu when copying a cred
Date: Sat, 14 Nov 2026 05:38:02 +0000 [thread overview]
Message-ID: <sashiko-outbox-214186@kernel.org> (raw)
In-Reply-To: <20261114052900.7-1-bbnpreetsingh@gmail.com>
> prepare_creds() copies the current cred while another task can be in
> get_cred() on it, clearing non_rcu. KCSAN reports:
>
> BUG: KCSAN: data-race in io_prep_async_work / prepare_creds
>
> write to 0xffff8881046cea68 of 4 bytes by task 3646 on cpu 1:
> get_cred_many include/linux/cred.h:222 [inline]
> get_cred include/linux/cred.h:238 [inline]
> io_prep_async_work+0x9b/0x3c0 io_uring/io_uring.c:367
>
> read to 0xffff8881046ce9c0 of 184 bytes by task 3645 on cpu 0:
> prepare_creds+0x71/0x550 kernel/cred.c:192
>
> The race is harmless. non_rcu and usage are the only fields that change
> on a published cred, and both are reset on the new cred right after the
> copy.
>
> Annotate the copy with data_race(). prepare_kernel_cred() makes the
> same copy, so annotate it too and switch it to memcpy() to match.
>
> Reported-by: syzbot+ee58b040032d8bed63d9@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=ee58b040032d8bed63d9
> Reported-by: syzbot+557fdc985d6ac3831e14@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=557fdc985d6ac3831e14
> Signed-off-by: Babanpreet Singh <bbnpreetsingh@gmail.com>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261114052900.7-1-bbnpreetsingh@gmail.com?part=1
prev parent reply other threads:[~2026-11-14 5:38 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-14 5:29 [PATCH v2] cred: annotate data race on non_rcu when copying a cred Babanpreet Singh
2026-11-14 5:38 ` sashiko-bot [this message]
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