Subject: [syzbot] [hams?] WARNING: refcount bug in ax25_release (3)

From: syzbot <[email-masked]>
Date: Sun, 26 May 2024 16:38:24 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    56fb6f92854f Merge tag 'drm-next-2024-05-25' of https://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17e2d748980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=34e05c35ec964e75
dashboard link: https://syzkaller.appspot.com/bug?extid=33841dc6aa3e1d86b78a
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/6f3028c1d0fa/disk-56fb6f92.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/81203e55e7d0/vmlinux-56fb6f92.xz
kernel image: https://storage.googleapis.com/syzbot-assets/37bf21eee59d/bzImage-56fb6f92.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

------------[ cut here ]------------
refcount_t: decrement hit 0; leaking memory.
WARNING: CPU: 1 PID: 19983 at lib/refcount.c:31 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:31
Modules linked in:
CPU: 1 PID: 19983 Comm: syz-executor.4 Not tainted 6.9.0-syzkaller-12277-g56fb6f92854f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
RIP: 0010:refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:31
Code: b2 00 00 00 e8 27 b8 ef fc 5b 5d c3 cc cc cc cc e8 1b b8 ef fc c6 05 fc 35 f0 0a 01 90 48 c7 c7 a0 bf 1e 8c e8 47 e8 b1 fc 90 <0f> 0b 90 90 eb d9 e8 fb b7 ef fc c6 05 d9 35 f0 0a 01 90 48 c7 c7
RSP: 0018:ffffc9001b83f908 EFLAGS: 00010246
RAX: 2a301f9112304400 RBX: ffff88807b02a664 RCX: 0000000000040000
RDX: ffffc9000b33b000 RSI: 000000000000ca38 RDI: 000000000000ca39
RBP: 0000000000000004 R08: ffffffff815846c2 R09: 1ffffffff25ededb
R10: dffffc0000000000 R11: fffffbfff25ededc R12: ffff88807b02a620
R13: 0000000000000000 R14: ffff88807b02a664 R15: dffffc0000000000
FS:  00007f475dfe66c0(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff2b9901723 CR3: 000000007ac0a000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_dec include/linux/refcount.h:336 [inline]
 refcount_dec include/linux/refcount.h:351 [inline]
 ref_tracker_free+0x6af/0x7e0 lib/ref_tracker.c:236
 netdev_tracker_free include/linux/netdevice.h:4058 [inline]
 netdev_put include/linux/netdevice.h:4075 [inline]
 ax25_release+0x368/0x950 net/ax25/af_ax25.c:1069
 __sock_release net/socket.c:659 [inline]
 sock_close+0xbc/0x240 net/socket.c:1421
 __fput+0x406/0x8b0 fs/file_table.c:422
 task_work_run+0x24f/0x310 kernel/task_work.c:180
 get_signal+0x15e6/0x1740 kernel/signal.c:2681
 arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xc9/0x370 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f475d27cee9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f475dfe60c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: 0000000000000000 RBX: 00007f475d3ac050 RCX: 00007f475d27cee9
RDX: 0000000000000019 RSI: 0000000000000101 RDI: 0000000000000004
RBP: 00007f475d2c949e R08: 0000000000000010 R09: 0000000000000000
R10: 00000000200002c0 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f475d3ac050 R15: 00007ffd8cfeadc8
 </TASK>

---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email-masked].

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup