From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-172.mta0.migadu.com (out-172.mta0.migadu.com [91.218.175.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E427F3F822F for ; Thu, 11 Jun 2026 12:37:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781181461; cv=none; b=C4a0MaovGhtwDYImHhbh3yDr91lifXdYp06AIexLnyEMWzzZYHNPnN7ZlMSs/aYjbGTEZ5ipbkX+WNtWCcspTHY4zWjfj0ljSFKz/tTmgSVKpDXXfJBTtgGfcydqC+bzEOwhWy94AZCeZRZqClyPvIC29F4x5I4n0ojt8kPXWJg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781181461; c=relaxed/simple; bh=fb6F9NbHGOOkl1ukNjB3RxWEVAw93TVPUsKKFrWd/cc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ObHQES7jFr33XvbWUP+bwYrdk8mXigetRoSO9NcvGIa6tOQFzKV2fwmGAv99cuRLulekjo+ECIYZPrqh7XwJ3oDi472HDO7hvwX4AFQr/DPJPrLO/kqQAw7up4lBhdDUJ8RJzGjeJoLzGgF84wu8NQ7BxYM4bJHk+1UX5Ebm/fg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=sL7cfOWN; arc=none smtp.client-ip=91.218.175.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="sL7cfOWN" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1781181457; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SnKin/8QWY0K4/Ln1YsJgi/WrSjXVk81XeuZsV2Spuk=; b=sL7cfOWNlpxWOn/oUGwIVG8app5HtUvEJj/lQTzVWuzYrFJaXFDPVfF2f+iqEWDOxxZp5w uE16w9wh7ntuRvVf1alSi7C+2JLxbkg8L0ZihroPYBH/5CtEesTNdQlnSLB0XSLUG0+y4t SfjCqr4Y4rgLcIFWVuc+k7uK88X7Z+E= From: Jiayuan Chen To: bpf@vger.kernel.org Cc: Weiming Shi , Xiang Mei , Xinyu Ma , Jiayuan Chen , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , John Fastabend , Stanislav Fomichev , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jakub Sitnicki , Shuah Khan , Jesper Dangaard Brouer , Sechang Lim , Ihor Solodrai , Cong Wang , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf v2 1/7] bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() Date: Thu, 11 Jun 2026 20:34:09 +0800 Message-ID: <20260611123538.156005-2-jiayuan.chen@linux.dev> In-Reply-To: <20260611123538.156005-1-jiayuan.chen@linux.dev> References: <20260611123538.156005-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Weiming Shi 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 Reviewed-by: Jiayuan Chen Cc: Jiayuan Chen Signed-off-by: Weiming Shi --- To sashiko: Regarding bpf_msg_push_data() reading "copy = msg->sg.data[i].length" with i == msg->sg.end (appending at the very end of a full/near-full ring): This is pre-existing code, not touched by this series, and reproducing it needs a narrow combination -- a pure append at the end so the loop exits with i == msg->sg.end, a full/near-full ring, plus a prior push/pop history that leaves a stale length in the otherwise-unused end slot. A freshly built ring zeroes that slot, so copy stays 0. We don't consider it practically reproducible. Even then it's already covered: the overflow check in patch 1 ("copy + len < copy") rejects the dangerous case, and __GFP_ZERO in patch 3 prevents any data exposure. Not worth fixing here. --- net/core/filter.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/core/filter.c b/net/core/filter.c index 9590877b0714f..3c8f1cedb217f 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2829,6 +2829,9 @@ 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