[syzbot] [net?] WARNING: refcount bug in nsim_fib_event_nb

[syzbot <syzbot+ed81dabfbde89a6311b5@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    d759ee240d3c Merge tag 'net-6.11-rc7' of git://git.kernel...
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=17166f29980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=660f6eb11f9c7dc5
dashboard link: https://syzkaller.appspot.com/bug?extid=ed81dabfbde89a6311b5
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d0ae115b9910/disk-d759ee24.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5c4b4ce8a5a5/vmlinux-d759ee24.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b98d3ce897eb/bzImage-d759ee24.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ed81dabfbde89a6311b5@syzkaller.appspotmail.com

------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 6557 at lib/refcount.c:25 refcount_warn_saturate+0x13a/0x1d0 lib/refcount.c:25
Modules linked in:
CPU: 0 UID: 0 PID: 6557 Comm: kworker/u8:16 Not tainted 6.11.0-rc6-syzkaller-00178-gd759ee240d3c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Workqueue: netns cleanup_net
RIP: 0010:refcount_warn_saturate+0x13a/0x1d0 lib/refcount.c:25
Code: a0 3a 60 8c e8 d7 2d a3 fc 90 0f 0b 90 90 eb b9 e8 9b 09 e1 fc c6 05 d2 c4 4f 0b 01 90 48 c7 c7 00 3b 60 8c e8 b7 2d a3 fc 90 <0f> 0b 90 90 eb 99 e8 7b 09 e1 fc c6 05 b3 c4 4f 0b 01 90 48 c7 c7
RSP: 0018:ffffc90014d973a0 EFLAGS: 00010246
RAX: ccfc4fa8067d8700 RBX: ffff888025a89a3c RCX: ffff888035538000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffffffff8155b372 R09: fffffbfff1cfa0e0
R10: dffffc0000000000 R11: fffffbfff1cfa0e0 R12: ffffffffffffffff
R13: ffff88805e847000 R14: ffff888025a89a3c R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8880b8800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff487f626e0 CR3: 000000002b560000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_inc include/linux/refcount.h:241 [inline]
 refcount_inc include/linux/refcount.h:258 [inline]
 fib_info_hold include/net/ip_fib.h:606 [inline]
 nsim_fib4_prepare_event drivers/net/netdevsim/fib.c:930 [inline]
 nsim_fib_event_schedule_work drivers/net/netdevsim/fib.c:1000 [inline]
 nsim_fib_event_nb+0xee9/0x10b0 drivers/net/netdevsim/fib.c:1043
 call_fib_notifier+0x42/0x70 net/core/fib_notifier.c:24
 call_fib_entry_notifier net/ipv4/fib_trie.c:90 [inline]
 fib_leaf_notify net/ipv4/fib_trie.c:2204 [inline]
 fib_table_notify net/ipv4/fib_trie.c:2222 [inline]
 fib_notify+0x445/0x780 net/ipv4/fib_trie.c:2245
 fib_net_dump net/core/fib_notifier.c:71 [inline]
 register_fib_notifier+0x182/0x370 net/core/fib_notifier.c:109
 nsim_fib_create+0x902/0xa70 drivers/net/netdevsim/fib.c:1595
 nsim_dev_reload_create drivers/net/netdevsim/dev.c:1480 [inline]
 nsim_dev_reload_up+0x3d1/0x8e0 drivers/net/netdevsim/dev.c:985
 devlink_reload+0x478/0x870 net/devlink/dev.c:474
 devlink_pernet_pre_exit+0x1f3/0x440 net/devlink/core.c:509
 ops_pre_exit_list net/core/net_namespace.c:163 [inline]
 cleanup_net+0x615/0xcc0 net/core/net_namespace.c:620
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd10 kernel/workqueue.c:3389
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>


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