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 4A0D031A7EA; Fri, 9 Jan 2026 12:28:51 +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=1767961731; cv=none; b=TSUthL+rRwyXrqhz05PNcZ0R0gSE/dHaKqGwqAAcHVpqmVaL3D4Q5tDOz74X/j0Hssy20h//pWzPbOi6OCDTQ+r2y3IcYvjpnBuDB04DEvzKVCWCprtfQ0KWokw2hdZOE+DsFBexRYCvm4b2gS1H0kTmuEz0o19ND3ddUVb1Qzs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767961731; c=relaxed/simple; bh=BPsRORkfo1nkhwnOlKqtYKHLsXaueMbarBU5xgMbpo4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=g11p9wJ5ceJl1ZMRFham0A777b9zMSdFixOudi8YwhPFsbtMvcCySf+tVF4B/4aI62S673VWyIuoo3YVdbDhtErZAsKGrJW57pHjsNWsq+Yh+vWNWYLBn7npB8N17NGiHKEouJNR8G1yeskDjzq7CJwascdk6EcBD/16SIBWavQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TqIjX+3W; 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="TqIjX+3W" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CBCB9C4CEF1; Fri, 9 Jan 2026 12:28:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767961731; bh=BPsRORkfo1nkhwnOlKqtYKHLsXaueMbarBU5xgMbpo4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TqIjX+3W/6S6PCx7JvxbZD2RmBAo9DFBx8HNFOtFDTA181Pua1cEvyGqtGRrmizfb E6kkTIALxaA25R4TO5MQL2N89ff1jn9fNhUi2tah06O7Fa573WFd1H+QpaqA/K3mOy uWQu/IvnROJYmtEjAOmxObbNwsEByZohOu4J4KyA= 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 6.1 117/634] bpf: Check skb->transport_header is set in bpf_skb_check_mtu Date: Fri, 9 Jan 2026 12:36:35 +0100 Message-ID: <20260109112121.836481609@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260109112117.407257400@linuxfoundation.org> References: <20260109112117.407257400@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 6.1-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 786064ac889a1..ac84e70cf5436 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6206,9 +6206,12 @@ 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