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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: John Fastabend , Stanislav Fomichev , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Hao Luo , Jiri Olsa , Simon Horman , bpf@vger.kernel.org, netdev@vger.kernel.org, Xiang Mei , Weiming Shi Subject: [PATCH bpf] bpf, sockmap: Fix wrong rsge offset in bpf_msg_push_data() Date: Thu, 23 Apr 2026 08:58:08 -0700 Message-ID: <20260423155807.1245644-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When bpf_msg_push_data() splits a scatterlist element into head and tail, the tail's page offset is advanced by `start` (absolute message byte offset) instead of `start - offset` (byte position within the element). This makes rsge.offset overshoot by `offset` bytes, pointing to the wrong location within the page or beyond its boundary. Consumers of the corrupted entry either silently read wrong data or trigger an out-of-bounds access. BUG: KASAN: slab-use-after-free in bpf_msg_pull_data (net/core/filter.c:2728) Read of size 32752 at addr ffff8881042f0010 by task poc/130 Call Trace: __asan_memcpy (mm/kasan/shadow.c:105) bpf_msg_pull_data (net/core/filter.c:2728) bpf_prog_run_pin_on_cpu (include/linux/bpf.h:1402) sk_psock_msg_verdict (net/core/skmsg.c:934) tcp_bpf_send_verdict (net/ipv4/tcp_bpf.c:421) sock_sendmsg_nosec (net/socket.c:727) Fixes: 6fff607e2f14 ("bpf: sk_msg program helper bpf_msg_push_data") Reported-by: Xiang Mei Signed-off-by: Weiming Shi --- net/core/filter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/filter.c b/net/core/filter.c index 3e56b567bd18..f12fbc49bc03 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2865,7 +2865,7 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start, psge->length = start - offset; rsge.length -= psge->length; - rsge.offset += start; + rsge.offset += start - offset; sk_msg_iter_var_next(i); sg_unmark_end(psge); -- 2.43.0