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 91ED6417D7E; Thu, 30 Jul 2026 15:21:00 +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=1785424861; cv=none; b=Y9x+cF5uYjCHIgN7HEG7iJlUTELSIOXHPnTeYVRIHHLPLUr2bJ4zfnyEuIVvwC8/F4AgoCHM0cm9TCw1znL1H8cKySuevGMDXr6q8xdWcoN9Edau3c0DzguxF/BCfIfGM2/j99hhhYUNR97Yqk5reF5wjuMXx1s2pztf8EpAPYA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785424861; c=relaxed/simple; bh=XnjMvshd75d6/0R3OvyzP5/7z+ADQTJAXwGXud1n+dc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MvAn/ADidcdfLcqkN8i8fId5I8ELKYpmaNdZ5KsT2cl7SjLMus591heVgsk7Thy9kG4k1YmN+sx+L5qHczYl4/oO4Lo2x2r8wMzrXdvSeVSZJKTgJccEAZ8/JxnRWlgqZM+Aa42cP03AM7o1X8xhm6T7/R06G1l1vt4zjOp7y78= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=bTR8mqfR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="bTR8mqfR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC5801F00ACF; Thu, 30 Jul 2026 15:20:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785424860; bh=xYpgfKiSC8PpxDZwvBM0XG/ss99tMruo3LJkgW+kgmU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=bTR8mqfR7/xZ17j9ouB83EVbbKYEHenxzuPogDQEZmkdH2TnmrRcOaBsU2NHs6EU4 ifqcvl7ohOwlP6koiE7RiyIfuF7yGTT2jByt4dyLuwIEIE8GwRp88ZJPeqYIBcMjLE kt5f7DOQfPe1wDXO17lH5sWFnjMAh6P57cP1fwtc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Shiming Cheng , Willem de Bruijn , Jakub Kicinski Subject: [PATCH 6.18 541/675] net: gro: fix double aggregation of flush-marked skbs Date: Thu, 30 Jul 2026 16:14:31 +0200 Message-ID: <20260730141456.642338100@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141445.110192266@linuxfoundation.org> References: <20260730141445.110192266@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Shiming Cheng commit e751256486d0ded20f5a9f9863467f1dce65142f upstream. 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: Greg Kroah-Hartman --- net/core/gro.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/net/core/gro.c +++ b/net/core/gro.c @@ -231,7 +231,9 @@ done: 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 (!pskb_may_pull(skb, skb_gro_offset(skb))) {