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([147.46.174.222]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-37d1600975asm1087971a91.0.2026.06.19.19.44.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Jun 2026 19:44:41 -0700 (PDT) From: Sechang Lim To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , John Fastabend , Jakub Sitnicki , Eduard Zingerman Cc: Eric Dumazet , Kuniyuki Iwashima , Paolo Abeni , Willem de Bruijn , "David S . Miller" , Jakub Kicinski , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Kumar Kartikeya Dwivedi , Simon Horman , Shuah Khan , Jiayuan Chen , Bobby Eshleman , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next v5 1/3] selftests/bpf: don't modify the skb in the strparser parser prog Date: Sat, 20 Jun 2026 02:44:16 +0000 Message-ID: <20260620024423.4141004-2-rhkrqnwk98@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260620024423.4141004-1-rhkrqnwk98@gmail.com> References: <20260620024423.4141004-1-rhkrqnwk98@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit sockmap_parse_prog.c is attached as an SK_SKB stream parser and modifies the skb: it calls bpf_skb_pull_data() and writes a byte into the packet. A stream parser runs on strparser's message head and must not modify it. A resize frees the frag_list segments strparser still tracks, leading to a use-after-free. Make the parser read-only. It only needs to return the message length, which keeps it attaching once packet-modifying parsers are rejected. Reviewed-by: Jiayuan Chen Signed-off-by: Sechang Lim --- .../selftests/bpf/progs/sockmap_parse_prog.c | 22 ------------------- 1 file changed, 22 deletions(-) diff --git a/tools/testing/selftests/bpf/progs/sockmap_parse_prog.c b/tools/testing/selftests/bpf/progs/sockmap_parse_prog.c index c9abfe3a11af..56e9aebf05f2 100644 --- a/tools/testing/selftests/bpf/progs/sockmap_parse_prog.c +++ b/tools/testing/selftests/bpf/progs/sockmap_parse_prog.c @@ -5,28 +5,6 @@ SEC("sk_skb1") int bpf_prog1(struct __sk_buff *skb) { - void *data_end = (void *)(long) skb->data_end; - void *data = (void *)(long) skb->data; - __u8 *d = data; - int err; - - if (data + 10 > data_end) { - err = bpf_skb_pull_data(skb, 10); - if (err) - return SK_DROP; - - data_end = (void *)(long)skb->data_end; - data = (void *)(long)skb->data; - if (data + 10 > data_end) - return SK_DROP; - } - - /* This write/read is a bit pointless but tests the verifier and - * strparser handler for read/write pkt data and access into sk - * fields. - */ - d = data; - d[7] = 1; return skb->len; } -- 2.43.0