syzbot
WARNING: refcount bug in config_item_get
Status:
upstream: reported C repro on 2026/07/28 10:20
Reported-by: syzbot+fc32b6c2798db135badf@syzkaller.appspotmail.com
First crash: 11d, last: 6h35m
Sample crash report:
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 1 PID: 4779 at lib/refcount.c:25 refcount_warn_saturate+0xff/0x1a0 lib/refcount.c:25
Modules linked in:
CPU: 1 PID: 4779 Comm: syz.1.305 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:refcount_warn_saturate+0xff/0x1a0 lib/refcount.c:25
Code: 09 01 48 c7 c7 40 1b df 8a e8 1d fb 37 fd 0f 0b eb e0 e8 c4 70 6c fd c6 05 55 e3 f6 09 01 48 c7 c7 80 1a df 8a e8 01 fb 37 fd <0f> 0b eb c4 e8 a8 70 6c fd c6 05 3a e3 f6 09 01 48 c7 c7 e0 1a df
RSP: 0018:ffffc900055c7c68 EFLAGS: 00010246
RAX: 0fafc45e0622dd00 RBX: 0000000000000002 RCX: ffff888075259e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: 0000000000000000 R08: ffff8880b8f279db R09: 1ffff110171e4f3b
R10: dffffc0000000000 R11: ffffed10171e4f3c R12: ffff88802a8a35b0
R13: dffffc0000000000 R14: 0000000000000002 R15: ffff88807720d000
FS: 0000555586e69500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000040 CR3: 000000005e165000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__refcount_add include/linux/refcount.h:-1 [inline]
__refcount_inc include/linux/refcount.h:250 [inline]
refcount_inc include/linux/refcount.h:267 [inline]
kref_get include/linux/kref.h:45 [inline]
config_item_get+0x7f/0x90 fs/configfs/item.c:104
configfs_get_config_item fs/configfs/configfs_internal.h:128 [inline]
get_target fs/configfs/symlink.c:125 [inline]
configfs_symlink+0x463/0x13c0 fs/configfs/symlink.c:191
vfs_symlink+0x245/0x3d0 fs/namei.c:4479
do_symlinkat+0x1b6/0x400 fs/namei.c:4508
__do_sys_symlinkat fs/namei.c:4525 [inline]
__se_sys_symlinkat fs/namei.c:4522 [inline]
__x64_sys_symlinkat+0x95/0xa0 fs/namei.c:4522
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f1d1659e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcba132408 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f1d16825fa0 RCX: 00007f1d1659e0d9
RDX: 0000200000000200 RSI: ffffffffffffff9c RDI: 00002000000001c0
RBP: 00007f1d16635024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1d16825fac R14: 00007f1d16825fa0 R15: 00007f1d16825fa0
</TASK>
* Struck through repros no longer work on HEAD.