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AFNElJ+SES21b5DmMG2M80Y1dbEZYDZN5XT2+t6jXQb0B1rLOwLLnULwNOBdrhuVTw6+7GVISXvSixg=@vger.kernel.org X-Gm-Message-State: AOJu0Ywf/chmQjiDyP+7c1Dz3+TyvpH3gzS+xfwuyK+7RNiAU+npTdQP x7X9QE4RJh3pydlvEZS9PvHdioHNm2DdVz2lBLCulgqO3+yGkwMg5Xdsc+D5eevbKV2lAkWM3vF QPN7fRg== X-Received: from pfbmy11-n1.prod.google.com ([2002:a05:6a00:6d4b:10b0:842:4be5:5ed6]) (user=kuniyu job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:3c84:b0:841:dca1:8b69 with SMTP id d2e1a72fcca58-844e193a47cmr2006688b3a.5.1781311260910; Fri, 12 Jun 2026 17:41:00 -0700 (PDT) Date: Sat, 13 Jun 2026 00:40:41 +0000 In-Reply-To: <20260612130919.299124-5-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260612130919.299124-5-jiayuan.chen@linux.dev> X-Mailer: git-send-email 2.54.0.1136.gdb2ca164c4-goog Message-ID: <20260613004059.1345029-1-kuniyu@google.com> Subject: Re: [PATCH bpf-next v3 4/7] bpf, sockmap: keep sk_msg copy state in sync From: Kuniyuki Iwashima To: jiayuan.chen@linux.dev Cc: 2045gemini@gmail.com, andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, cong.wang@bytedance.com, daniel@iogearbox.net, davem@davemloft.net, eddyz87@gmail.com, edumazet@google.com, emil@etsalapatis.com, hawk@kernel.org, horms@kernel.org, ihor.solodrai@linux.dev, jakub@cloudflare.com, john.fastabend@gmail.com, jolsa@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, martin.lau@linux.dev, memxor@gmail.com, netdev@vger.kernel.org, pabeni@redhat.com, rhkrqnwk98@gmail.com, rollkingzzc@gmail.com, sdf@fomichev.me, shuah@kernel.org, song@kernel.org, stable@vger.kernel.org, yonghong.song@linux.dev, Kuniyuki Iwashima Content-Type: text/plain; charset="UTF-8" From: Jiayuan Chen Date: Fri, 12 Jun 2026 21:07:48 +0800 > From: Zhang Cen > > SK_MSG uses msg->sg.copy as per-scatterlist-entry provenance. Entries > with this bit set are copied before data/data_end are exposed to SK_MSG > BPF programs for direct packet access. > > bpf_msg_pull_data(), bpf_msg_push_data(), and bpf_msg_pop_data() > rewrite the sk_msg scatterlist ring by collapsing, splitting, and > shifting entries. These operations move msg->sg.data[] entries, but the > parallel copy bitmap can be left behind on the old slot. A copied entry > can then return to msg->sg.start with its copy bit clear and be exposed > as directly writable packet data. > > This corruption path requires an attached SK_MSG BPF program that calls > the mutating helpers; ordinary sockmap/TLS traffic that never runs > push/pop/pull helper sequences is not affected. > > Keep msg->sg.copy synchronized with scatterlist entry moves, preserve > the copy bit when an entry is split, clear it when a helper replaces an > entry with a private page, and clear slots vacated by pull-data > compaction. > > Fixes: 015632bb30da ("bpf: sk_msg program helper bpf_sk_msg_pull_data") > Fixes: 6fff607e2f14 ("bpf: sk_msg program helper bpf_msg_push_data") > Fixes: 7246d8ed4dcc ("bpf: helper to pop data from messages") > Cc: stable@vger.kernel.org > Co-developed-by: Han Guidong <2045gemini@gmail.com> > Reviewed-by: John Fastabend > Reviewed-by: Emil Tsalapatis > Signed-off-by: Han Guidong <2045gemini@gmail.com> > Signed-off-by: Zhang Cen > Signed-off-by: Jiayuan Chen Reviewed-by: Kuniyuki Iwashima