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 7D62733CE9A; Fri, 9 Jan 2026 12:02:12 +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=1767960132; cv=none; b=CuJrfPXRSDrRmEMVAgw0zjjCA7OlEOEuXQ8j1NayD7xLNhOLZAktHudUz8JXkkEoilbOESsHN4fQnlA4D9gT7kz+UISXRvBWRyV1heuqMyfXk2YrOf0PWlXfod8KJBmM2l/YSU57haDWNnJyFOcCa3/8HscDdnVoW/l2qOnhpko= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767960132; c=relaxed/simple; bh=VFNAFV9XbwgbcMAKJaS59QN96soPJ51AeerjUhTqujg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oDsIM1c7qeUwQpMFPohz8HILo5zGICHMU9XGHDpsv4PTjIpeZfMH37g8wkqDKGoYRNfQT4NwqXkRhe0qgLmdtvXsOvqyyhjYWM4DGnRIbYNkYcGc+2bB1BCxDs5VTJ7o9rtO/AOwW1PrivXck8x32oXrRBAGj7QM/z6Jdr70wng= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=b1XcU1d8; 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="b1XcU1d8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0624EC4CEF1; Fri, 9 Jan 2026 12:02:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767960132; bh=VFNAFV9XbwgbcMAKJaS59QN96soPJ51AeerjUhTqujg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b1XcU1d8B3dmu2momCqzVA9jzHnCcAx+b50kSM4LBzhI1fwAbiOJiV7OJ2jysaK5z 6vmn/4MFnmgyIJWD1gmf2t/CBePijM3Ekmplx3mTqRD3cy6YByJhseGyCYCwbmOlP4 AmCesGVYHy3yEx4EwHJfr5Cp2tKuHisaSz5UAp5o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+1de74b0794c40c8eb300@syzkaller.appspotmail.com, Eric Dumazet , Kui-Feng Lee , David Ahern , "David S. Miller" Subject: [PATCH 6.6 297/737] ipv6: avoid possible NULL deref in modify_prefix_route() Date: Fri, 9 Jan 2026 12:37:16 +0100 Message-ID: <20260109112145.182344920@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260109112133.973195406@linuxfoundation.org> References: <20260109112133.973195406@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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet commit a747e02430dfb3657141f99aa6b09331283fa493 upstream. syzbot found a NULL deref [1] in modify_prefix_route(), caused by one fib6_info without a fib6_table pointer set. This can happen for net->ipv6.fib6_null_entry [1] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] CPU: 1 UID: 0 PID: 5837 Comm: syz-executor888 Not tainted 6.12.0-syzkaller-09567-g7eef7e306d3c #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 RIP: 0010:__lock_acquire+0xe4/0x3c40 kernel/locking/lockdep.c:5089 Code: 08 84 d2 0f 85 15 14 00 00 44 8b 0d ca 98 f5 0e 45 85 c9 0f 84 b4 0e 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 96 2c 00 00 49 8b 04 24 48 3d a0 07 7f 93 0f 84 RSP: 0018:ffffc900035d7268 EFLAGS: 00010006 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000006 RSI: 1ffff920006bae5f RDI: 0000000000000030 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001 R10: ffffffff90608e17 R11: 0000000000000001 R12: 0000000000000030 R13: ffff888036334880 R14: 0000000000000000 R15: 0000000000000000 FS: 0000555579e90380(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffc59cc4278 CR3: 0000000072b54000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] modify_prefix_route+0x30b/0x8b0 net/ipv6/addrconf.c:4831 inet6_addr_modify net/ipv6/addrconf.c:4923 [inline] inet6_rtm_newaddr+0x12c7/0x1ab0 net/ipv6/addrconf.c:5055 rtnetlink_rcv_msg+0x3c7/0xea0 net/core/rtnetlink.c:6920 netlink_rcv_skb+0x16b/0x440 net/netlink/af_netlink.c:2541 netlink_unicast_kernel net/netlink/af_netlink.c:1321 [inline] netlink_unicast+0x53c/0x7f0 net/netlink/af_netlink.c:1347 netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1891 sock_sendmsg_nosec net/socket.c:711 [inline] __sock_sendmsg net/socket.c:726 [inline] ____sys_sendmsg+0xaaf/0xc90 net/socket.c:2583 ___sys_sendmsg+0x135/0x1e0 net/socket.c:2637 __sys_sendmsg+0x16e/0x220 net/socket.c:2669 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fd1dcef8b79 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffc59cc4378 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fd1dcef8b79 RDX: 0000000000040040 RSI: 0000000020000140 RDI: 0000000000000004 RBP: 00000000000113fd R08: 0000000000000006 R09: 0000000000000006 R10: 0000000000000006 R11: 0000000000000246 R12: 00007ffc59cc438c R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001 Fixes: 5eb902b8e719 ("net/ipv6: Remove expired routes with a separated list of routes.") Reported-by: syzbot+1de74b0794c40c8eb300@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/67461f7f.050a0220.1286eb.0021.GAE@google.com/T/#u Signed-off-by: Eric Dumazet CC: Kui-Feng Lee Cc: David Ahern Reviewed-by: David Ahern Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/addrconf.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -4784,7 +4784,7 @@ inet6_rtm_deladdr(struct sk_buff *skb, s ifm->ifa_prefixlen, extack); } -static int modify_prefix_route(struct inet6_ifaddr *ifp, +static int modify_prefix_route(struct net *net, struct inet6_ifaddr *ifp, unsigned long expires, u32 flags, bool modify_peer) { @@ -4808,7 +4808,9 @@ static int modify_prefix_route(struct in ifp->prefix_len, ifp->rt_priority, ifp->idev->dev, expires, flags, GFP_KERNEL); - } else { + return 0; + } + if (f6i != net->ipv6.fib6_null_entry) { table = f6i->fib6_table; spin_lock_bh(&table->tb6_lock); @@ -4821,9 +4823,8 @@ static int modify_prefix_route(struct in } spin_unlock_bh(&table->tb6_lock); - - fib6_info_release(f6i); } + fib6_info_release(f6i); return 0; } @@ -4902,7 +4903,7 @@ static int inet6_addr_modify(struct net int rc = -ENOENT; if (had_prefixroute) - rc = modify_prefix_route(ifp, expires, flags, false); + rc = modify_prefix_route(net, ifp, expires, flags, false); /* prefix route could have been deleted; if so restore it */ if (rc == -ENOENT) { @@ -4912,7 +4913,7 @@ static int inet6_addr_modify(struct net } if (had_prefixroute && !ipv6_addr_any(&ifp->peer_addr)) - rc = modify_prefix_route(ifp, expires, flags, true); + rc = modify_prefix_route(net, ifp, expires, flags, true); if (rc == -ENOENT && !ipv6_addr_any(&ifp->peer_addr)) { addrconf_prefix_route(&ifp->peer_addr, ifp->prefix_len,