From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 3F2482F12D4; Fri, 9 Jan 2026 11:55:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767959746; cv=none; b=O4Abh2h3qY6+vaTKRX3r/LqDAuCkVvbVj7S6A3Qg8nr2VN4mBSaZ4b41o5NkMhKj4uK8i5SUH5FLdp5bO4vX+/KiCyVnvR+Q0AoTWHkQ857l6Y5ZPmrDkH/fuqUJg767JElvoN6dSVkFwgyJaoOwJJv8pORD6NngJ6t3djWi9Zk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767959746; c=relaxed/simple; bh=TDFUFgZsMbrnCYXAO/Y6mv8cBrImIbRzpvIpfbgVJRo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=avnQaXVhmKCBrzUutoKhDd5aOlL/8LNDEYR8WhQ/ySqAdX/XkKnj04ev2+vA0P+y0WqAT+Zsrk1mvl4vA7pfndnHAHpwgXcJdEeWML84Ic0TkHS52fhBFqoIbfAPqrP3Ec8Li0lAa5O4uHffuT6W5V8TWIZ+UvCzW7fF9wohgYo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BrSVSo0r; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="BrSVSo0r" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BE1EAC4CEF1; Fri, 9 Jan 2026 11:55:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767959746; bh=TDFUFgZsMbrnCYXAO/Y6mv8cBrImIbRzpvIpfbgVJRo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BrSVSo0rFIhjAcq8oW4H6TNVOSkKLBktGBAadcLACPbLsxq5dum9YTgg1CrNc48ks YKBdbG1EgF0yy1bp8fm49MRHZOc4aOZuK2zgSSfuap7MJiBPE5y9z8uRWlDFp0zQpI gDdLP5gzqc2Mh0tAiBnseXUfcOYY1H3A7q/CJ2yQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jesper Dangaard Brouer , Kaiyan Mei , Yinhao Hu , Martin KaFai Lau , Alexei Starovoitov , Sasha Levin Subject: [PATCH 6.6 160/737] bpf: Check skb->transport_header is set in bpf_skb_check_mtu Date: Fri, 9 Jan 2026 12:34:59 +0100 Message-ID: <20260109112140.014265364@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260109112133.973195406@linuxfoundation.org> References: <20260109112133.973195406@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Martin KaFai Lau [ Upstream commit d946f3c98328171fa50ddb908593cf833587f725 ] The bpf_skb_check_mtu helper needs to use skb->transport_header when the BPF_MTU_CHK_SEGS flag is used: bpf_skb_check_mtu(skb, ifindex, &mtu_len, 0, BPF_MTU_CHK_SEGS) The transport_header is not always set. There is a WARN_ON_ONCE report when CONFIG_DEBUG_NET is enabled + skb->gso_size is set + bpf_prog_test_run is used: WARNING: CPU: 1 PID: 2216 at ./include/linux/skbuff.h:3071 skb_gso_validate_network_len bpf_skb_check_mtu bpf_prog_3920e25740a41171_tc_chk_segs_flag # A test in the next patch bpf_test_run bpf_prog_test_run_skb For a normal ingress skb (not test_run), skb_reset_transport_header is performed but there is plan to avoid setting it as described in commit 2170a1f09148 ("net: no longer reset transport_header in __netif_receive_skb_core()"). This patch fixes the bpf helper by checking skb_transport_header_was_set(). The check is done just before skb->transport_header is used, to avoid breaking the existing bpf prog. The WARN_ON_ONCE is limited to bpf_prog_test_run, so targeting bpf-next. Fixes: 34b2021cc616 ("bpf: Add BPF-helper for MTU checking") Cc: Jesper Dangaard Brouer Reported-by: Kaiyan Mei Reported-by: Yinhao Hu Signed-off-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20251112232331.1566074-1-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- net/core/filter.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 0564ee6ac8731..da1a617b7db94 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6295,9 +6295,12 @@ BPF_CALL_5(bpf_skb_check_mtu, struct sk_buff *, skb, */ if (skb_is_gso(skb)) { ret = BPF_MTU_CHK_RET_SUCCESS; - if (flags & BPF_MTU_CHK_SEGS && - !skb_gso_validate_network_len(skb, mtu)) - ret = BPF_MTU_CHK_RET_SEGS_TOOBIG; + if (flags & BPF_MTU_CHK_SEGS) { + if (!skb_transport_header_was_set(skb)) + return -EINVAL; + if (!skb_gso_validate_network_len(skb, mtu)) + ret = BPF_MTU_CHK_RET_SEGS_TOOBIG; + } } out: *mtu_len = mtu; -- 2.51.0