syzbot


WARNING: refcount bug in ax25_release

Status: upstream: reported on 2025/06/28 14:27
Reported-by: syzbot+c4481f358c239cae7335@syzkaller.appspotmail.com
First crash: 67d, last: 43d
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 WARNING: refcount bug in ax25_release origin:upstream 13 C error 44 14d 445d 0/3 upstream: reported C repro on 2024/06/15 15:04
upstream WARNING: refcount bug in ax25_release (3) hams 13 C done 5256 160d 465d 28/29 fixed on 2025/06/10 16:19
upstream WARNING: refcount bug in ax25_release hams 13 1 722d 722d 0/29 closed as invalid on 2023/12/15 13:48
upstream WARNING: refcount bug in ax25_release (2) hams 13 C 240 469d 534d 25/29 fixed on 2024/05/22 23:16

Sample crash report:
------------[ cut here ]------------
refcount_t: decrement hit 0; leaking memory.
WARNING: CPU: 1 PID: 16521 at lib/refcount.c:31 refcount_warn_saturate+0x147/0x1b0 lib/refcount.c:31
Modules linked in:
CPU: 1 PID: 16521 Comm: syz.0.2507 Not tainted 6.6.99-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:refcount_warn_saturate+0x147/0x1b0 lib/refcount.c:31
Code: 0a 01 48 c7 c7 e0 0d fc 8a e8 f5 c2 31 fd 0f 0b eb a8 e8 4c 4e 67 fd c6 05 9e db 16 0a 01 48 c7 c7 00 0f fc 8a e8 d9 c2 31 fd <0f> 0b eb 8c e8 30 4e 67 fd c6 05 7f db 16 0a 01 48 c7 c7 e0 0d fc
RSP: 0018:ffffc9001a9f7b48 EFLAGS: 00010246
RAX: 8f8d306c06f91100 RBX: 0000000000000004 RCX: ffff88802971da00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: ffffc9001a9f7ca0 R08: ffffffff90da264f R09: 1ffffffff21b44c9
R10: dffffc0000000000 R11: fffffbfff21b44ca R12: ffff8880790485b8
R13: dffffc0000000000 R14: ffff8880790485fc R15: 0000000000000001
FS:  000055557de2f500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2da07ff8 CR3: 000000007e2da000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 __refcount_dec include/linux/refcount.h:344 [inline]
 refcount_dec include/linux/refcount.h:359 [inline]
 ref_tracker_free+0x698/0x7d0 lib/ref_tracker.c:236
 netdev_tracker_free include/linux/netdevice.h:4130 [inline]
 netdev_put include/linux/netdevice.h:4147 [inline]
 ax25_release+0x356/0x930 net/ax25/af_ax25.c:1080
 __sock_release net/socket.c:659 [inline]
 sock_close+0xbd/0x230 net/socket.c:1421
 __fput+0x234/0x970 fs/file_table.c:384
 task_work_run+0x1ce/0x250 kernel/task_work.c:239
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa32878e9a9
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:00007ffc9d88ae58 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fa3289b7ba0 RCX: 00007fa32878e9a9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fa3289b7ba0 R08: 000000000001809c R09: 0000001a9d88b14f
R10: 00007fa3289b7ac0 R11: 0000000000000246 R12: 00000000001636da
R13: 00007fa3289b6160 R14: ffffffffffffffff R15: 00007ffc9d88af70
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/22 20:06 linux-6.6.y d96eb99e2f0e 8e9d1dc1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING: refcount bug in ax25_release
2025/07/12 04:39 linux-6.6.y 59a2de10b81a 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING: refcount bug in ax25_release
2025/06/28 14:26 linux-6.6.y 3f5b4c104b7d fc9d8ee5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING: refcount bug in ax25_release
* Struck through repros no longer work on HEAD.