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 7260B392C44; Wed, 21 Jan 2026 18:28:58 +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=1769020138; cv=none; b=T1/NWp22ZQN10nG7EMwypde19RUMTWsvN3tz0qdLsLAAxLma1TXJkmbW/vrs49FcjBPmWpr1jXnDwUtOaTp/1hRd5rfqUKGHhDGzig3MmvJha7vDDY9seg4u6GzT0uyT71tWDNFo4+mhzv4fiz1iPp2RtlsKMOsvDCeYa+j0Onw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769020138; c=relaxed/simple; bh=AygbOAci50Id99JbOsksVb36vvMhvX6guIL44RI2Xhk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OrQYfA/Tp9h9Cz6wwpKf/3HkwA7zc2nL6XrYFeWz65XG6p3pL/FzRl9592vTLQUqnCwett9lXBeB/N64/bSsLhr2dgQLdqEwOiLNRM8jTBUa2BltqZKj0Fl6YDIqIxgYC0dIhA55C6MDJC834Izt9xc1fVZ8X8oDS/pGRhpnJWA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=F5MweGVd; 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="F5MweGVd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BD158C16AAE; Wed, 21 Jan 2026 18:28:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1769020138; bh=AygbOAci50Id99JbOsksVb36vvMhvX6guIL44RI2Xhk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=F5MweGVd+Xnp+WeH3aWbquumVv/ZDAP2k2fasnNdweGxO4dxLaBWFQqBNf1Kxj6F6 lgaEr99+tzCEaOebah1cN0Lavqh1Ek911sJRwflLenszeV9Pt44TMN484LUD4/tgae zQ8nNuoxbe3H471aHKIdS0S036Yjd87gFHMKzOb0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+7c134e1c3aa3283790b9@syzkaller.appspotmail.com, Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18 037/198] ipv4: ip_gre: make ipgre_header() robust Date: Wed, 21 Jan 2026 19:14:25 +0100 Message-ID: <20260121181419.885699729@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260121181418.537774329@linuxfoundation.org> References: <20260121181418.537774329@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit e67c577d89894811ce4dcd1a9ed29d8b63476667 ] Analog to commit db5b4e39c4e6 ("ip6_gre: make ip6gre_header() robust") Over the years, syzbot found many ways to crash the kernel in ipgre_header() [1]. This involves team or bonding drivers ability to dynamically change their dev->needed_headroom and/or dev->hard_header_len In this particular crash mld_newpack() allocated an skb with a too small reserve/headroom, and by the time mld_sendpack() was called, syzbot managed to attach an ipgre device. [1] skbuff: skb_under_panic: text:ffffffff89ea3cb7 len:2030915468 put:2030915372 head:ffff888058b43000 data:ffff887fdfa6e194 tail:0x120 end:0x6c0 dev:team0 kernel BUG at net/core/skbuff.c:213 ! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 1 UID: 0 PID: 1322 Comm: kworker/1:9 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Workqueue: mld mld_ifc_work RIP: 0010:skb_panic+0x157/0x160 net/core/skbuff.c:213 Call Trace: skb_under_panic net/core/skbuff.c:223 [inline] skb_push+0xc3/0xe0 net/core/skbuff.c:2641 ipgre_header+0x67/0x290 net/ipv4/ip_gre.c:897 dev_hard_header include/linux/netdevice.h:3436 [inline] neigh_connected_output+0x286/0x460 net/core/neighbour.c:1618 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247 NF_HOOK+0x9e/0x380 include/linux/netfilter.h:318 mld_sendpack+0x8d4/0xe60 net/ipv6/mcast.c:1855 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2693 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 Fixes: c54419321455 ("GRE: Refactor GRE tunneling code.") Reported-by: syzbot+7c134e1c3aa3283790b9@syzkaller.appspotmail.com Closes: https://www.spinics.net/lists/netdev/msg1147302.html Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260108190214.1667040-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv4/ip_gre.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index 8178c44a3cdd4..e13244729ad8d 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -891,10 +891,17 @@ static int ipgre_header(struct sk_buff *skb, struct net_device *dev, const void *daddr, const void *saddr, unsigned int len) { struct ip_tunnel *t = netdev_priv(dev); - struct iphdr *iph; struct gre_base_hdr *greh; + struct iphdr *iph; + int needed; + + needed = t->hlen + sizeof(*iph); + if (skb_headroom(skb) < needed && + pskb_expand_head(skb, HH_DATA_ALIGN(needed - skb_headroom(skb)), + 0, GFP_ATOMIC)) + return -needed; - iph = skb_push(skb, t->hlen + sizeof(*iph)); + iph = skb_push(skb, needed); greh = (struct gre_base_hdr *)(iph+1); greh->flags = gre_tnl_flags_to_gre_flags(t->parms.o_flags); greh->protocol = htons(type); -- 2.51.0