From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta0.migadu.com (out-188.mta0.migadu.com [91.218.175.188]) (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 BE04E3F7A94 for ; Thu, 11 Jun 2026 12:37:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781181480; cv=none; b=YlR6gT2H4kymh3ym2Y6KFRBGcHMpmTJIzxQaHx1+qaVkMBjVdasTbp/LQFBwpmeWHH17IQLVQ4U81vjH4YiyfK5wfHo7sB2FjRAkHX+YGaEVE8wVlGOfeDEe79s+q+Pr1iDfS/tgC0Cunc0flOpbpQAZb/B9O+Xvomr4GpnNpm4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781181480; c=relaxed/simple; bh=Mz/dtjJFB8K7mJFgV3aWCEtTQaLdZpwGy4k7t9rfP/0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IFNZ1M46MSo4uAzCpR/pPSaZ9qGrPNJwRGnlMR3qmWoUfhK82INVYw41RYj1x6snMZVOiLWCTL89HzVZ1dz2kKIrfg/KtwshqANlLhqqQqhKUkFU6nuJfZzmYJJ3EssFNM/Ahb6jbXy9qOEBiHynxO5alSidU5wGPosZBSLJVxk= 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=uXNsy4+K; arc=none smtp.client-ip=91.218.175.188 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="uXNsy4+K" 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=1781181475; 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=gomvGYWAOkigl2R+ikTsOAyD89SbDoYkSYMX3yIK3Sk=; b=uXNsy4+KkBI+0TlaauVRKwmvdIrvxgx8TJi4A6Vxq6zoM8WmN1fQ6mpAO7lTzLytrQWXUS wo9qf7XTyf/CaF0pt4k4qivQEY9D92uU9NRhtyogKdXhYsTsdY9JGL4BTW27+xHSbuFnjZ CCEJDYQwC2azGrn/zG6r9KOetW7kl1k= From: Jiayuan Chen To: bpf@vger.kernel.org Cc: Weiming Shi , Xiang Mei , Jiayuan Chen , Daniel Borkmann , John Fastabend , Stanislav Fomichev , Martin KaFai Lau , Alexei Starovoitov , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , "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 2/7] bpf, sockmap: Fix wrong rsge offset in bpf_msg_push_data() Date: Thu, 11 Jun 2026 20:34:10 +0800 Message-ID: <20260611123538.156005-3-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 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 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 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/filter.c b/net/core/filter.c index 3c8f1cedb217f..3e555f276ba80 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); -- 2.43.0