From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 911654195A1 for ; Sat, 8 Aug 2026 14:09:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786198186; cv=none; b=j84cRoeRUDUiKrT/sxUwxQLqBIj4n2kEL7ymhLAGls+bWs6SJueHYSMG2CkbcpCyVztzr1/3TtwztxWjmRkcd1y21kA69GhlmkjhDMJY/P9kTsseS2lggbfMCzIDcLAroR2Wc/QS9JgsW7ILWsFiZWnEk3zSx2N//izAxIrL1/A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786198186; c=relaxed/simple; bh=QMql+FyFHfOW5W4wjOCrXh0hDseyyyEtOXOWytK9DDw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ja3RXPTTtP0219Ro8Zvh4a/Xg6hCnxqlrI18gCK/fLktYFq9ANsvfW76bEmn3fnbVyOMR/JGgcJDAZ+MH2anh1BAjCUnC0Py86b+sFQH/myTnyUFNEqso2EJLuTQL2CxBW5QhYNItRg6VOxnlKt74rGhpZNVKG4SsAJwQdNe9ww= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ibc4naOL; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ibc4naOL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9A501F00A3A; Sat, 8 Aug 2026 14:09:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786198184; bh=sATf4Etpqgkp9pJY31uhLnCEbEhoT84Atz/oveUKRzo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ibc4naOLIZMlXFyuC5otr5OMMp/pLH2WaY5iZQhLgXrhy2804rgqo72z/rbyleRps UmLjqk1FvbR81x6j+2uUDEyJuuhrupicJrMmm94l59BV25HinHhmnqc4E4/RR0g471 yOLE3wfJQXUrRO5zx0gnsb9GnrFdA5moyWmyH16N/zHaD5gtC00rPtaxDcHTkGI1I+ cjOB2hllBZnjFbSTilr9SKprhMDyLyoPsjmhcT8ppxNZalowccg6qIs/L1p/VPWUCb PCrVWGLeyt2ME5hc91a3VqtGZQlttKtkAgLjsTefcddGMeOYQ7320onWDNaDrHYVwi ZhEGKD2tXLL5A== From: Sasha Levin To: stable@vger.kernel.org Cc: Shiming Cheng , Willem de Bruijn , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.1.y 2/2] net: gro: fix double aggregation of flush-marked skbs Date: Sat, 8 Aug 2026 10:09:41 -0400 Message-ID: <20260808140941.339987-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260808140941.339987-1-sashal@kernel.org> References: <2026072946-itunes-reviver-5817@gregkh> <20260808140941.339987-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Shiming Cheng [ Upstream commit e751256486d0ded20f5a9f9863467f1dce65142f ] Commit 0ab03f353d36 ("net-gro: Fix GRO flush when receiving a GSO packet.") added a flush check to skb_gro_receive(), but skb_gro_receive_list() lacks the same validation. As a result, packets marked with NAPI_GRO_CB(skb)->flush may still be re-aggregated. This allows already-GRO'd packets with existing frag_list to be re-aggregated into a new GRO session, corrupting the frag_list chain structure. When skb_segment() attempts to unpack these malformed packets, it encounters invalid state and triggers a kernel panic. Scenario (Tethering/Device forwarding): 1. Driver: Generated aggregated packet P1 via LRO with frag_list 2. Dev A: Receives aggregated fraglist packet and flush flag set 3. Dev A: Re-enters GRO, skb_gro_receive_list() is called 4. Missing flush check allows re-aggregation despite flush flag 5. Frag_list chain becomes corrupted (loops or dangling refs) 6. Dev B: TX path calls skb_segment(), crashes on corrupted frag_list Root cause in skb_segment(): The check at line ~4891: if (hsize <= 0 && i >= nfrags && skb_headlen(list_skb) && (skb_headlen(list_skb) == len || sg)) { When frag_list is corrupted by double aggregation, when list_skb is a NULL pointer from skb->next, skb_headlen(list_skb) dereference NULL/corrupted pointers occurs. Call Trace: skb_headlen(NULL skb) skb_segment tcp_gso_segment tcp4_gso_segment inet_gso_segment skb_mac_gso_segment __skb_gso_segment skb_gso_segment validate_xmit_skb validate_xmit_skb_list sch_direct_xmit qdisc_restart __qdisc_run qdisc_run net_tx_action Fix: Add NAPI_GRO_CB(skb)->flush validation to the early-return check in skb_gro_receive_list(), matching the defensive programming pattern of skb_gro_receive(). Fixes: 3a1296a38d0c ("net: Support GRO/GSO fraglist chaining.") Cc: stable@vger.kernel.org Signed-off-by: Shiming Cheng Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260709014704.3625-1-shiming.cheng@mediatek.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/core/gro.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/core/gro.c b/net/core/gro.c index 79e81889fcc4d..855ffaaea54f4 100644 --- a/net/core/gro.c +++ b/net/core/gro.c @@ -297,7 +297,9 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb) int skb_gro_receive_list(struct sk_buff *p, struct sk_buff *skb) { - if (unlikely(p->len + skb->len >= 65536)) + /* make sure to check flush flag and to not merge */ + if (unlikely(p->len + skb->len >= 65536 || + NAPI_GRO_CB(skb)->flush)) return -E2BIG; if (NAPI_GRO_CB(p)->last == p) -- 2.53.0