[syzbot] [netfilter?] WARNING in nft_socket_init (2)

[syzbot] [netfilter?] WARNING in nft_socket_init (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    94619ea2d933 Merge tag 'ipsec-next-2025-07-23' of git://gi..
git tree:       net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14bf10a2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ceda48240b85ec34
dashboard link: https://syzkaller.appspot.com/bug?extid=a225fea35d7baf8dbdc3
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12bf10a2580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13d27fd4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/afd64d9816ee/disk-94619ea2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e1755ce1f83b/vmlinux-94619ea2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2061dff2fbf4/bzImage-94619ea2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a225fea35d7baf8dbdc3@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 5853 at net/netfilter/nft_socket.c:220 nft_socket_init+0x2f4/0x3d0 net/netfilter/nft_socket.c:220
Modules linked in:
CPU: 0 UID: 0 PID: 5853 Comm: syz-executor145 Not tainted 6.16.0-rc6-syzkaller-01673-g94619ea2d933 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:nft_socket_init+0x2f4/0x3d0 net/netfilter/nft_socket.c:220
Code: 84 c0 0f 85 da 00 00 00 41 88 2c 24 bd 08 00 00 00 e9 ad fe ff ff 89 f3 e8 29 86 07 f8 89 d8 e9 57 ff ff ff e8 1d 86 07 f8 90 <0f> 0b 90 e9 44 ff ff ff 89 e9 80 e1 07 38 c1 0f 8c 87 fd ff ff 48
RSP: 0018:ffffc9000401f178 EFLAGS: 00010293
RAX: ffffffff89b8a433 RBX: ffff888077f68020 RCX: ffff888030a8da00
RDX: 0000000000000000 RSI: 0000000000000100 RDI: 00000000000000ff
RBP: 00000000000000ff R08: 0000000000000000 R09: ffffffff89b8b21c
R10: dffffc0000000000 R11: ffffed10299a8e5b R12: 0000000000000100
R13: ffff8880352ec898 R14: dffffc0000000000 R15: 1ffff1100efed004
FS:  000055555942b380(0000) GS:ffff888125c15000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000000 CR3: 0000000034702000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 nf_tables_newexpr net/netfilter/nf_tables_api.c:3496 [inline]
 nf_tables_newrule+0x178f/0x2890 net/netfilter/nf_tables_api.c:4327
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:524 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:647 [inline]
 nfnetlink_rcv+0x112f/0x2520 net/netfilter/nfnetlink.c:665
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x82c/0x9e0 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:714 [inline]
 __sock_sendmsg+0x219/0x270 net/socket.c:729
 ____sys_sendmsg+0x505/0x830 net/socket.c:2614
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2668
 __sys_sendmsg net/socket.c:2700 [inline]
 __do_sys_sendmsg net/socket.c:2705 [inline]
 __se_sys_sendmsg net/socket.c:2703 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2703
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7efdcf55c0e9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 18 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:00007fff48ea8a28 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007efdcf55c0e9
RDX: 0000000000000000 RSI: 0000200000000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007efdcf5a5036
R13: 00007fff48ea8a60 R14: 00007fff48ea8aa0 R15: 0000000000000000
 </TASK>


---
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Re: [syzbot] [netfilter?] WARNING in nft_socket_init (2)

[Pablo Neira Ayuso]

[-- Attachment #1: Type: text/plain, Size: 1208 bytes --]

On Fri, Jul 25, 2025 at 05:46:30AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    94619ea2d933 Merge tag 'ipsec-next-2025-07-23' of git://gi..
> git tree:       net-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=14bf10a2580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ceda48240b85ec34
> dashboard link: https://syzkaller.appspot.com/bug?extid=a225fea35d7baf8dbdc3
> compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12bf10a2580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13d27fd4580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/afd64d9816ee/disk-94619ea2.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/e1755ce1f83b/vmlinux-94619ea2.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/2061dff2fbf4/bzImage-94619ea2.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+a225fea35d7baf8dbdc3@syzkaller.appspotmail.com

Attached patch should fix this.

[-- Attachment #2: fix.patch --]
[-- Type: text/x-diff, Size: 409 bytes --]

diff --git a/net/netfilter/nft_socket.c b/net/netfilter/nft_socket.c
index 35d0409b0095..36affbb697c2 100644
--- a/net/netfilter/nft_socket.c
+++ b/net/netfilter/nft_socket.c
@@ -217,7 +217,7 @@ static int nft_socket_init(const struct nft_ctx *ctx,
 
 		level += err;
 		/* Implies a giant cgroup tree */
-		if (WARN_ON_ONCE(level > 255))
+		if (level > 255)
 			return -EOPNOTSUPP;
 
 		priv->level = level;

Re: [syzbot] [netfilter?] WARNING in nft_socket_init (2)

[Florian Westphal]

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> Attached patch should fix this.

Yes, jus removing the WARN is the correct way.

Re: [syzbot] [netfilter?] WARNING in nft_socket_init (2)

[syzbot]

syzbot has bisected this issue to:

commit 7f3287db654395f9c5ddd246325ff7889f550286
Author: Florian Westphal <fw@strlen.de>
Date:   Sat Sep 7 14:07:49 2024 +0000

    netfilter: nft_socket: make cgroupsv2 matching work with namespaces

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17ff50a2580000
start commit:   94619ea2d933 Merge tag 'ipsec-next-2025-07-23' of git://gi..
git tree:       net-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1400d0a2580000
console output: https://syzkaller.appspot.com/x/log.txt?x=1000d0a2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ceda48240b85ec34
dashboard link: https://syzkaller.appspot.com/bug?extid=a225fea35d7baf8dbdc3
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12bf10a2580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13d27fd4580000

Reported-by: syzbot+a225fea35d7baf8dbdc3@syzkaller.appspotmail.com
Fixes: 7f3287db6543 ("netfilter: nft_socket: make cgroupsv2 matching work with namespaces")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection