From: Weiming Shi Date: Mon, 15 Jun 2026 02:19:55 +0000 (+0800) Subject: bpf, sockmap: Fix wrong rsge offset in bpf_msg_push_data() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f3f34ca45b96c21722204e30576fd29db8f1aff7;p=thirdparty%2Flinux.git bpf, sockmap: Fix wrong rsge offset in bpf_msg_push_data() 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 Reviewed-by: Jiayuan Chen Reviewed-by: Emil Tsalapatis Reviewed-by: Kuniyuki Iwashima Signed-off-by: Weiming Shi Signed-off-by: Jiayuan Chen Link: https://lore.kernel.org/r/20260615021959.140010-3-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov --- diff --git a/net/core/filter.c b/net/core/filter.c index 4b159045881d..978e740792be 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2872,7 +2872,7 @@ 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);