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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: John Fastabend , Stanislav Fomichev , Song Liu , Yonghong Song , Jiri Olsa , Simon Horman , bpf@vger.kernel.org, netdev@vger.kernel.org, Xiang Mei , Weiming Shi , Xinyu Ma Subject: [PATCH bpf] bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() Date: Fri, 24 Apr 2026 12:16:04 -0700 Message-ID: <20260424191602.1522411-3-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 the scatterlist ring is full or nearly full, bpf_msg_push_data() enters a copy fallback path and computes copy + len for the page allocation size. Since len comes from BPF with arg3_type = ARG_ANYTHING and both are u32, a crafted len can wrap the sum to a small value, causing an undersized allocation followed by an out-of-bounds memcpy. BUG: unable to handle page fault for address: ffffed104089a402 Oops: Oops: 0000 [#1] SMP KASAN NOPTI Call Trace: __asan_memcpy (mm/kasan/shadow.c:105) bpf_msg_push_data (net/core/filter.c:2852 net/core/filter.c:2788) bpf_prog_9ed8b5711920a7d7+0x2e/0x36 sk_psock_msg_verdict (net/core/skmsg.c:934) tcp_bpf_sendmsg (net/ipv4/tcp_bpf.c:421 net/ipv4/tcp_bpf.c:584) __sys_sendto (net/socket.c:2206) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Add an overflow check before the allocation. Link: https://lore.kernel.org/all/20260424155913.A19FDC19425@smtp.kernel.org Fixes: 6fff607e2f14 ("bpf: sk_msg program helper bpf_msg_push_data") Tested-by: Xiang Mei Tested-by: Xinyu Ma Signed-off-by: Weiming Shi --- net/core/filter.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/core/filter.c b/net/core/filter.c index bc96c18df4e0..4f5a00ade2d3 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2820,6 +2820,9 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start, if (!space || (space == 1 && start != offset)) copy = msg->sg.data[i].length; + if (unlikely(copy + len < copy)) + return -EINVAL; + page = alloc_pages(__GFP_NOWARN | GFP_ATOMIC | __GFP_COMP, get_order(copy + len)); if (unlikely(!page)) -- 2.43.0