linux-kernel - Re: [syzbot] [hams?] possible deadlock in nr_rt

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Message-ID: <685d58f2.a00a0220.34b642.0110.GAE@google.com>
Date: Thu, 26 Jun 2025 07:28:02 -0700
From: syzbot <syzbot+14afda08dc3484d5db82@...kaller.appspotmail.com>
To: eadavis@...com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [hams?] possible deadlock in nr_rt_ioctl (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in nr_remove_node_locked

------------[ cut here ]------------
WARNING: CPU: 2 PID: 6679 at net/netrom/nr_route.c:290 nr_remove_node_locked+0x1b3/0x200 net/netrom/nr_route.c:290
Modules linked in:
CPU: 2 UID: 0 PID: 6679 Comm: syz.0.45 Not tainted 6.16.0-rc3-syzkaller-gee88bddf7f2f-dirty #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:nr_remove_node_locked+0x1b3/0x200 net/netrom/nr_route.c:290
Code: be ff ff ff ff 48 c7 c7 58 50 59 90 e8 46 dc 10 01 31 ff 89 c5 89 c6 e8 6b 65 4f f7 85 ed 0f 85 a4 fe ff ff e8 1e 6a 4f f7 90 <0f> 0b 90 e9 96 fe ff ff 48 c7 c7 44 2d a7 90 e8 e9 47 b6 f7 e9 6e
RSP: 0018:ffffc90003b47ab0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff888025854f00 RCX: ffffffff8a6cb3d5
RDX: ffff8880442a0000 RSI: ffffffff8a6cb3e2 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
R13: ffff88803c362000 R14: ffff888026762c00 R15: 0000000000000000
FS:  00007f21787756c0(0000) GS:ffff8880d6974000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e55ffff CR3: 000000004f9b7000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 nr_del_node net/netrom/nr_route.c:347 [inline]
 nr_rt_ioctl+0x1fc7/0x26f0 net/netrom/nr_route.c:675
 nr_ioctl+0x19a/0x2e0 net/netrom/af_netrom.c:1254
 sock_do_ioctl+0x115/0x280 net/socket.c:1190
 sock_ioctl+0x227/0x6b0 net/socket.c:1311
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl fs/ioctl.c:893 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2177985d29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2178775038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f2177b75fa0 RCX: 00007f2177985d29
RDX: 0000000020000180 RSI: 000000000000890c RDI: 0000000000000005
RBP: 00007f2177a01b08 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f2177b75fa0 R15: 00007fff2cb7c2d8
 </TASK>


Tested on:

commit:         ee88bddf Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=170adb70580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=644a0493ff5118b1
dashboard link: https://syzkaller.appspot.com/bug?extid=14afda08dc3484d5db82
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=116bb182580000