From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Nicholas Dudar" <main.kalliope@gmail.com>, <ast@kernel.org>,
<daniel@iogearbox.net>, <andrii@kernel.org>, <eddyz87@gmail.com>,
<memxor@gmail.com>, <akpm@linux-foundation.org>
Cc: <martin.lau@linux.dev>, <song@kernel.org>,
<yonghong.song@linux.dev>, <jolsa@kernel.org>,
<emil@etsalapatis.com>, <ihor.solodrai@linux.dev>,
<davem@davemloft.net>, <bpf@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <deller@gmx.de>
Subject: Re: [PATCH bpf] bpf: Fix page double free in test_bpf skb setup
Date: Thu, 17 Sep 2026 03:11:30 +0000 [thread overview]
Message-ID: <DLH9GNAO4JH7.Q7DM1I60M8TP@gmail.com> (raw)
In-Reply-To: <20260917023834.2760055-1-main.kalliope@gmail.com>
On Thu Sep 17, 2026 at 2:38 AM UTC, Nicholas Dudar wrote:
> build_test_skb() transfers page ownership to an skb with
> skb_add_rx_frag(). If either allocation in the second loop iteration fails,
> kfree_skb() releases page[0], but the error path then falls through and
> frees page[0] again.
>
> Return after freeing skb[0], since page[0] is already owned by the skb at
> that point; the raw page cleanup is only correct for the first iteration.
>
> Fixes: 76db8087c4c9 ("net: bpf: add a test for skb_segment in test_bpf module")
> Assisted-by: Codex:gpt-6-astra
> Signed-off-by: Nicholas Dudar <main.kalliope@gmail.com>
> ---
> Please queue this fix for stable. The double-free has been present since
> v4.17 and is reachable when the test_bpf skb test encounters an allocation
> failure.
No.
I don't think you have a way to reproduce it.
We don't scream "bug... apply to stable" just because AI found a tiny
race.
pw-bot: cr
prev parent reply other threads:[~2026-09-17 3:11 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 2:38 [PATCH bpf] bpf: Fix page double free in test_bpf skb setup Nicholas Dudar
2026-09-17 3:11 ` Alexei Starovoitov [this message]
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