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 D293E2FDC4F; Tue, 12 Aug 2025 18:42:18 +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=1755024139; cv=none; b=EEjv/ehetzYmZZWw+mF7NX20SBGYSi3e3FzlXjYrXXzFKlBoDb7OoHA9xtZ6YCidXMA81PLbuBgDyx/6tzjRNSllN+04SChw0p3CF3CKZSY5RVU78iBm+RkvK0MZ1hk3/OfPQH4UNOIvNAPiJIQTKmxwUqJpV831T7c+9errnS8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755024139; c=relaxed/simple; bh=F/uR4qEkZYdwAe7ENcjmnf0r3s8jtZW4A1UR+saJUqA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=o+LY9F4Ag3/NHeB7G43o363IViDY0L5A0v+7pZmncYYbBASS+8XNtL+8ofdn68i7MrYwrVYJv+vTb3iaVVPX2VWuJJJElCslt1pbK/RQtJhacVmEvBLFIvdIBvyaxep12e3hy7zZMu+4B9gMZvq3NrTwoDA4xSDqLmiiLQtstfE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=pEEmouIx; 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="pEEmouIx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E2B60C4CEF0; Tue, 12 Aug 2025 18:42:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755024138; bh=F/uR4qEkZYdwAe7ENcjmnf0r3s8jtZW4A1UR+saJUqA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pEEmouIxkJeOTm5QFiUo2q3pUe/Uf/bG/tfh9WPPk1FpsHSH5/h6Kwa7j26MOs1By 8W3381F91LzKIRoJ0YR63fLFDivTa7GwgDK67hDBz9UvisqmPpkSU40JyCKDfjIIQ8 G3I1k1GnRvanN1LD618nLAuK+vtm2TZbLGE+UHw4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , syzbot , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.16 286/627] ipv6: add a retry logic in net6_rt_notify() Date: Tue, 12 Aug 2025 19:29:41 +0200 Message-ID: <20250812173430.194382260@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250812173419.303046420@linuxfoundation.org> References: <20250812173419.303046420@linuxfoundation.org> User-Agent: quilt/0.68 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 6.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit ea2f921db7a483a526058c5b5b8162edd88dabe5 ] inet6_rt_notify() can be called under RCU protection only. This means the route could be changed concurrently and rt6_fill_node() could return -EMSGSIZE. Re-size the skb when this happens and retry, removing one WARN_ON() that syzbot was able to trigger: WARNING: CPU: 3 PID: 6291 at net/ipv6/route.c:6342 inet6_rt_notify+0x475/0x4b0 net/ipv6/route.c:6342 Modules linked in: CPU: 3 UID: 0 PID: 6291 Comm: syz.0.77 Not tainted 6.16.0-rc7-syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:inet6_rt_notify+0x475/0x4b0 net/ipv6/route.c:6342 Code: fc ff ff e8 6d 52 ea f7 e9 47 fc ff ff 48 8b 7c 24 08 4c 89 04 24 e8 5a 52 ea f7 4c 8b 04 24 e9 94 fd ff ff e8 9c fe 84 f7 90 <0f> 0b 90 e9 bd fd ff ff e8 6e 52 ea f7 e9 bb fb ff ff 48 89 df e8 RSP: 0018:ffffc900035cf1d8 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffffc900035cf540 RCX: ffffffff8a36e790 RDX: ffff88802f7e8000 RSI: ffffffff8a36e9d4 RDI: 0000000000000005 RBP: ffff88803c230f00 R08: 0000000000000005 R09: 00000000ffffffa6 R10: 00000000ffffffa6 R11: 0000000000000001 R12: 00000000ffffffa6 R13: 0000000000000900 R14: ffff888032ea4100 R15: 0000000000000000 FS: 00007fac7b89a6c0(0000) GS:ffff8880d6a20000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fac7b899f98 CR3: 0000000034b3f000 CR4: 0000000000352ef0 Call Trace: ip6_route_mpath_notify+0xde/0x280 net/ipv6/route.c:5356 ip6_route_multipath_add+0x1181/0x1bd0 net/ipv6/route.c:5536 inet6_rtm_newroute+0xe4/0x1a0 net/ipv6/route.c:5647 rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6944 netlink_rcv_skb+0x155/0x420 net/netlink/af_netlink.c:2552 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x58d/0x850 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1896 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg net/socket.c:727 [inline] ____sys_sendmsg+0xa95/0xc70 net/socket.c:2566 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2620 Fixes: 169fd62799e8 ("ipv6: Get rid of RTNL for SIOCADDRT and RTM_NEWROUTE.") Signed-off-by: Eric Dumazet Reported-by: syzbot Link: https://patch.msgid.link/20250725140725.3626540-2-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv6/route.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 7b9e49be7164..38016f5b2291 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -6321,8 +6321,9 @@ static int inet6_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh, void inet6_rt_notify(int event, struct fib6_info *rt, struct nl_info *info, unsigned int nlm_flags) { - struct sk_buff *skb; struct net *net = info->nl_net; + struct sk_buff *skb; + size_t sz; u32 seq; int err; @@ -6330,17 +6331,21 @@ void inet6_rt_notify(int event, struct fib6_info *rt, struct nl_info *info, seq = info->nlh ? info->nlh->nlmsg_seq : 0; rcu_read_lock(); - - skb = nlmsg_new(rt6_nlmsg_size(rt), GFP_ATOMIC); + sz = rt6_nlmsg_size(rt); +retry: + skb = nlmsg_new(sz, GFP_ATOMIC); if (!skb) goto errout; err = rt6_fill_node(net, skb, rt, NULL, NULL, NULL, 0, event, info->portid, seq, nlm_flags); if (err < 0) { - /* -EMSGSIZE implies BUG in rt6_nlmsg_size() */ - WARN_ON(err == -EMSGSIZE); kfree_skb(skb); + /* -EMSGSIZE implies needed space grew under us. */ + if (err == -EMSGSIZE) { + sz = max(rt6_nlmsg_size(rt), sz << 1); + goto retry; + } goto errout; } -- 2.39.5