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[2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6507618cc31sm222081a12.24.2026.01.05.08.43.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 Jan 2026 08:43:50 -0800 (PST) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 18D1C407EDE; Mon, 05 Jan 2026 17:43:50 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: KaFai Wan , 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 , Kaiyan Mei , Dongliang Mu Subject: Re: [PATCH bpf-next 1/2] bpf, test_run: Fix user-memory-access vulnerability for LIVE_FRAMES In-Reply-To: <38dd70d77f8207395206564063b0a1a07dd1c6e7.camel@linux.dev> References: <20260104162350.347403-1-kafai.wan@linux.dev> <20260104162350.347403-2-kafai.wan@linux.dev> <87y0mc5obp.fsf@toke.dk> <38dd70d77f8207395206564063b0a1a07dd1c6e7.camel@linux.dev> X-Clacks-Overhead: GNU Terry Pratchett Date: Mon, 05 Jan 2026 17:43:50 +0100 Message-ID: <87ms2s57sp.fsf@toke.dk> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable KaFai Wan writes: > On Mon, 2026-01-05 at 11:46 +0100, Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> KaFai Wan writes: >>=20 >> > This fix reverts to the original version and ensures data_hard_start >> > correctly points to the xdp_frame structure, eliminating the security >> > risk. >>=20 >> 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 frame= s is=20 > 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