From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: KaFai Wan <kafai.wan@linux.dev>,
ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org,
yonghong.song@linux.dev, john.fastabend@gmail.com,
kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com,
jolsa@kernel.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, horms@kernel.org,
hawk@kernel.org, shuah@kernel.org, aleksander.lobakin@intel.com,
bpf@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Cc: Yinhao Hu <dddddd@hust.edu.cn>,
Kaiyan Mei <M202472210@hust.edu.cn>,
Dongliang Mu <dzm91@hust.edu.cn>
Subject: Re: [PATCH bpf-next 1/2] bpf, test_run: Fix user-memory-access vulnerability for LIVE_FRAMES
Date: Mon, 05 Jan 2026 17:43:50 +0100 [thread overview]
Message-ID: <87ms2s57sp.fsf@toke.dk> (raw)
In-Reply-To: <38dd70d77f8207395206564063b0a1a07dd1c6e7.camel@linux.dev>
KaFai Wan <kafai.wan@linux.dev> writes:
> On Mon, 2026-01-05 at 11:46 +0100, Toke Høiland-Jørgensen wrote:
>> KaFai Wan <kafai.wan@linux.dev> writes:
>>
>> > This fix reverts to the original version and ensures data_hard_start
>> > correctly points to the xdp_frame structure, eliminating the security
>> > risk.
>>
>> This is wrong. We should just be checking the meta_len on input to
>> account for the size of xdp_frame. I'll send a patch.
>
> Current version the actual limit of the max input meta_len for live frames is
> XDP_PACKET_HEADROOM - sizeof(struct xdp_frame), not
> XDP_PACKET_HEADROOM.
By "current version", you mean the patch I sent[0], right?
If so, that was deliberate: the stack limits the maximum data_meta size
to XDP_PACKET_HEADROOM - sizeof(struct xdp_frame), so there's no reason
not to do the same for bpf_prog_run(). And some chance that diverging
here will end up surfacing other bugs down the line.
-Toke
[0] https://lore.kernel.org/r/20260105114747.1358750-1-toke@redhat.com
next prev parent reply other threads:[~2026-01-05 16:43 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-18 10:43 bpf: xdp: unhandled error in xdp_test_run_init_page() leads to crash Yinhao Hu
2025-12-18 18:26 ` Martin KaFai Lau
2026-01-04 16:23 ` [PATCH bpf-next 0/2] bpf, test_run: Fix user-memory-access vulnerability for LIVE_FRAMES KaFai Wan
2026-01-04 16:23 ` [PATCH bpf-next 1/2] " KaFai Wan
2026-01-05 10:46 ` Toke Høiland-Jørgensen
2026-01-05 13:22 ` KaFai Wan
2026-01-05 16:43 ` Toke Høiland-Jørgensen [this message]
2026-01-06 13:53 ` KaFai Wan
2026-01-04 16:23 ` [PATCH bpf-next 2/2] selftests/bpf: Add test for xdp_md context with LIVE_FRAMES in BPF_PROG_TEST_RUN KaFai Wan
2026-01-05 8:07 ` [syzbot ci] Re: bpf, test_run: Fix user-memory-access vulnerability for LIVE_FRAMES syzbot ci
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