[Android 5.10] KASAN: use-after-free Write in config_item_put

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 50b3a256e550 Merge 5.10.260 into android13-5.10-lts
git tree: android13-5.10-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=12621449580000
kernel config: https://syzkaller.appspot.com/x/.config?x=57bdfa4a173e5087
dashboard link: https://syzkaller.appspot.com/bug?extid=26ec90f463db63510f1c
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12ce5632580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12df249e580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/34994db436ce/disk-50b3a256.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7855257a6b73/vmlinux-50b3a256.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6367ad2e120a/bzImage-50b3a256.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+26ec90...@syzkaller.appspotmail.com

RBP: 00007ff9cf04feaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff9cf242038 R14: 00007ff9cf241fa0 R15: 00007fff58709e08
---[ end trace f0442e3d7ca7e47b ]---
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_fetch_sub_release include/asm-generic/atomic-instrumented.h:220 [inline]
BUG: KASAN: use-after-free in __refcount_sub_and_test include/linux/refcount.h:272 [inline]
BUG: KASAN: use-after-free in __refcount_dec_and_test include/linux/refcount.h:315 [inline]
BUG: KASAN: use-after-free in refcount_dec_and_test include/linux/refcount.h:333 [inline]
BUG: KASAN: use-after-free in kref_put include/linux/kref.h:64 [inline]
BUG: KASAN: use-after-free in config_item_put+0x33/0x210 fs/configfs/item.c:151
Write of size 4 at addr ffff88811739701c by task syz.5.518/1430

CPU: 1 PID: 1430 Comm: syz.5.518 Tainted: G W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
__dump_stack+0x21/0x24 lib/dump_stack.c:77
dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:435 [inline]
kasan_report+0x100/0x140 mm/kasan/report.c:452
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189
__kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
atomic_fetch_sub_release include/asm-generic/atomic-instrumented.h:220 [inline]
__refcount_sub_and_test include/linux/refcount.h:272 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
kref_put include/linux/kref.h:64 [inline]
config_item_put+0x33/0x210 fs/configfs/item.c:151
configfs_symlink+0x4a6/0x1320 fs/configfs/symlink.c:212
vfs_symlink+0x339/0x4c0 fs/namei.c:4107
do_symlinkat+0x10e/0x3d0 fs/namei.c:4134
__do_sys_symlinkat fs/namei.c:4148 [inline]
__se_sys_symlinkat fs/namei.c:4145 [inline]
__x64_sys_symlinkat+0x7b/0x90 fs/namei.c:4145
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7ff9cefb9e99
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:00007ff9cee1b028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007ff9cf241fa0 RCX: 00007ff9cefb9e99
RDX: 0000200000000340 RSI: ffffffffffffff9c RDI: 0000200000000300
RBP: 00007ff9cf04feaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff9cf242038 R14: 00007ff9cf241fa0 R15: 00007fff58709e08

Allocated by task 1437:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:430 [inline]
____kasan_kmalloc mm/kasan/common.c:509 [inline]
__kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518
kasan_kmalloc include/linux/kasan.h:254 [inline]
kmem_cache_alloc_trace+0x179/0x2e0 mm/slub.c:2979
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:667 [inline]
afunc_alloc_inst+0x4c/0x310 drivers/usb/gadget/function/f_uac2.c:1393
try_get_usb_function_instance drivers/usb/gadget/functions.c:28 [inline]
usb_get_function_instance+0xe2/0x2f0 drivers/usb/gadget/functions.c:44
function_make+0x118/0x350 drivers/usb/gadget/configfs.c:636
configfs_mkdir+0x5d2/0xd90 fs/configfs/dir.c:1354
vfs_mkdir+0x42c/0x600 fs/namei.c:3798
do_mkdirat+0x14c/0x340 fs/namei.c:3820
__do_sys_mkdirat fs/namei.c:3831 [inline]
__se_sys_mkdirat fs/namei.c:3829 [inline]
__x64_sys_mkdirat+0x7b/0x90 fs/namei.c:3829
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 1437:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
kasan_slab_free include/linux/kasan.h:220 [inline]
slab_free_hook mm/slub.c:1600 [inline]
slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
slab_free mm/slub.c:3208 [inline]
kfree+0xc0/0x270 mm/slub.c:4196
afunc_free_inst+0x15/0x20 drivers/usb/gadget/function/f_uac2.c:1386
usb_put_function_instance+0x85/0xa0 drivers/usb/gadget/functions.c:77
f_uac2_attr_release+0x15/0x20 drivers/usb/gadget/function/f_uac2.c:1248
config_item_cleanup fs/configfs/item.c:130 [inline]
config_item_release fs/configfs/item.c:139 [inline]
kref_put include/linux/kref.h:65 [inline]
config_item_put+0x158/0x210 fs/configfs/item.c:151
configfs_rmdir+0x89f/0x960 fs/configfs/dir.c:1580
vfs_rmdir+0x1ab/0x3c0 fs/namei.c:3860
do_rmdir+0x232/0x630 fs/namei.c:3920
__do_sys_unlinkat fs/namei.c:4084 [inline]
__se_sys_unlinkat fs/namei.c:4078 [inline]
__x64_sys_unlinkat+0xc7/0xf0 fs/namei.c:4078
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff888117397000
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 28 bytes inside of
512-byte region [ffff888117397000, ffff888117397200)
The buggy address belongs to the page:
page:ffffea00045ce500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x117394
head:ffffea00045ce500 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea0004afc300 0000000500000005 ffff888100043080
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 97, ts 6010310959, free_ts 0
set_page_owner include/linux/page_owner.h:35 [inline]
post_alloc_hook mm/page_alloc.c:2456 [inline]
prep_new_page+0x176/0x190 mm/page_alloc.c:2462
get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
__alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
alloc_slab_page mm/slub.c:-1 [inline]
allocate_slab mm/slub.c:1813 [inline]
new_slab+0x84/0x3f0 mm/slub.c:1874
new_slab_objects mm/slub.c:2632 [inline]
___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
__slab_alloc+0x63/0xa0 mm/slub.c:2836
slab_alloc_node mm/slub.c:2918 [inline]
slab_alloc mm/slub.c:2960 [inline]
__kmalloc_track_caller+0x1e4/0x310 mm/slub.c:4541
__kmalloc_reserve net/core/skbuff.c:144 [inline]
__alloc_skb+0xdc/0x520 net/core/skbuff.c:212
alloc_skb include/linux/skbuff.h:1126 [inline]
alloc_skb_with_frags+0xa3/0x560 net/core/skbuff.c:6006
sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2393
unix_dgram_sendmsg+0x6f3/0x18f0 net/unix/af_unix.c:1725
sock_sendmsg_nosec net/socket.c:652 [inline]
__sock_sendmsg net/socket.c:664 [inline]
sock_write_iter+0x2a6/0x3a0 net/socket.c:1019
call_write_iter include/linux/fs.h:2066 [inline]
new_sync_write fs/read_write.c:518 [inline]
vfs_write+0x770/0xd70 fs/read_write.c:605
ksys_write+0x14a/0x260 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x7b/0x90 fs/read_write.c:667
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
page_owner free stack trace missing

Memory state around the buggy address:
ffff888117396f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888117396f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888117397000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888117397080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888117397100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 1430 at lib/refcount.c:28 refcount_warn_saturate+0x120/0x1a0 lib/refcount.c:28
Modules linked in:
CPU: 1 PID: 1430 Comm: syz.5.518 Tainted: G B W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:refcount_warn_saturate+0x120/0x1a0 lib/refcount.c:28
Code: 04 01 48 c7 c7 e0 48 40 85 e8 7c ca 3a 02 0f 0b eb c3 e8 73 89 26 ff c6 05 b1 75 82 04 01 48 c7 c7 40 49 40 85 e8 60 ca 3a 02 <0f> 0b eb a7 e8 57 89 26 ff c6 05 92 75 82 04 01 48 c7 c7 60 48 40
RSP: 0018:ffffc9000135fc78 EFLAGS: 00010246
RAX: cdbfb1a45e3c3d00 RBX: 0000000000000003 RCX: ffff888119b7e2c0
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc9000135fc88 R08: ffffc9000135f607 R09: fffff5200026bef4
R10: dffffc0000000000 R11: fffff5200026bec1 R12: 00000000ffffffea
R13: dffffc0000000000 R14: 0000000000000003 R15: 00000000c0000000
FS: 00007ff9cee1b6c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f20fa67f580 CR3: 000000012f017000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__refcount_sub_and_test include/linux/refcount.h:283 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
kref_put include/linux/kref.h:64 [inline]
config_item_put+0x200/0x210 fs/configfs/item.c:151
configfs_symlink+0x4a6/0x1320 fs/configfs/symlink.c:212
vfs_symlink+0x339/0x4c0 fs/namei.c:4107
do_symlinkat+0x10e/0x3d0 fs/namei.c:4134
__do_sys_symlinkat fs/namei.c:4148 [inline]
__se_sys_symlinkat fs/namei.c:4145 [inline]
__x64_sys_symlinkat+0x7b/0x90 fs/namei.c:4145
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7ff9cefb9e99
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:00007ff9cee1b028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007ff9cf241fa0 RCX: 00007ff9cefb9e99
RDX: 0000200000000340 RSI: ffffffffffffff9c RDI: 0000200000000300
RBP: 00007ff9cf04feaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff9cf242038 R14: 00007ff9cf241fa0 R15: 00007fff58709e08
---[ end trace f0442e3d7ca7e47c ]---


---
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 syzk...@googlegroups.com.

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 syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 61d896ee2a80 Revert "hdlc_ppp: sync per-proto timers befor..
git tree: android13-5.15-lts
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13c71e32580000
kernel config: https://syzkaller.appspot.com/x/.config?x=43676e801f1929a9
dashboard link: https://syzkaller.appspot.com/bug?extid=9debb7cf73b48e32a8e5

compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=160d15b9580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11ed4649580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bcb85cf50754/disk-61d896ee.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7e4ac22ab0e5/vmlinux-61d896ee.xz
kernel image: https://storage.googleapis.com/syzbot-assets/14b47a248e31/bzImage-61d896ee.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+9debb7...@syzkaller.appspotmail.com

R10: 00007ffebd69a88c R11: 0000000000000246 R12: 00007ffebd69a88c
R13: 00007ffebd69a8c0 R14: 00007ffebd69a8a0 R15: 0000000000000007
</TASK>
---[ end trace 3a037ca40251f3d6 ]---

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]

BUG: KASAN: use-after-free in atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:167 [inline]

BUG: KASAN: use-after-free in __refcount_sub_and_test include/linux/refcount.h:272 [inline]
BUG: KASAN: use-after-free in __refcount_dec_and_test include/linux/refcount.h:315 [inline]
BUG: KASAN: use-after-free in refcount_dec_and_test include/linux/refcount.h:333 [inline]
BUG: KASAN: use-after-free in kref_put include/linux/kref.h:64 [inline]

BUG: KASAN: use-after-free in config_item_put+0x33/0x210 fs/configfs/item.c:149
Write of size 4 at addr ffff88810b331c24 by task syz-executor280/345

CPU: 0 PID: 345 Comm: syz-executor280 Tainted: G W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
__dump_stack+0x21/0x30 lib/dump_stack.c:88
dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:427 [inline]
kasan_report+0x10f/0x150 mm/kasan/report.c:444

check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189
__kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]

atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:167 [inline]

__refcount_sub_and_test include/linux/refcount.h:272 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
kref_put include/linux/kref.h:64 [inline]

config_item_put+0x33/0x210 fs/configfs/item.c:149
configfs_symlink+0x4a6/0x1330 fs/configfs/symlink.c:212
vfs_symlink+0x29e/0x470 fs/namei.c:4437
do_symlinkat+0x24a/0x5d0 fs/namei.c:4466
__do_sys_symlinkat fs/namei.c:4483 [inline]
__se_sys_symlinkat fs/namei.c:4480 [inline]
__x64_sys_symlinkat+0x99/0xb0 fs/namei.c:4480
x64_sys_call+0x74b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:267
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7efd570a5429
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffebd69a858 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00000000000062ce RCX: 00007efd570a5429
RDX: 0000200000000300 RSI: 00000000ffffff9c RDI: 0000200000000200
RBP: 0000000000000000 R08: 00007ffebd69a88c R09: 00007ffebd69a88c
R10: 00007ffebd69a88c R11: 0000000000000246 R12: 00007ffebd69a88c
R13: 00007ffebd69a8c0 R14: 00007ffebd69a8a0 R15: 0000000000000007
</TASK>

Allocated by task 342:

kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:45 [inline]

set_alloc_info mm/kasan/common.c:433 [inline]
____kasan_kmalloc mm/kasan/common.c:512 [inline]
__kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:521
kasan_kmalloc include/linux/kasan.h:227 [inline]
kmem_cache_alloc_trace+0x119/0x270 mm/slub.c:3274
kmalloc include/linux/slab.h:619 [inline]
kzalloc include/linux/slab.h:750 [inline]
fsg_alloc_inst+0x61/0x5a0 drivers/usb/gadget/function/f_mass_storage.c:3392

try_get_usb_function_instance drivers/usb/gadget/functions.c:28 [inline]
usb_get_function_instance+0xe2/0x2f0 drivers/usb/gadget/functions.c:44

function_make+0x118/0x350 drivers/usb/gadget/configfs.c:642
configfs_mkdir+0x50a/0x9c0 fs/configfs/dir.c:1329
vfs_mkdir+0x38b/0x590 fs/namei.c:4073
do_mkdirat+0x174/0x4d0 fs/namei.c:4098
__do_sys_mkdirat fs/namei.c:4113 [inline]
__se_sys_mkdirat fs/namei.c:4111 [inline]
__x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4111
x64_sys_call+0x37e/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:259
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 344:

kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370

____kasan_slab_free+0x125/0x160 mm/kasan/common.c:365
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
kasan_slab_free include/linux/kasan.h:193 [inline]
slab_free_hook mm/slub.c:1728 [inline]
slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
slab_free mm/slub.c:3526 [inline]
kfree+0xc4/0x270 mm/slub.c:4588
fsg_free_inst+0x33c/0x420 drivers/usb/gadget/function/f_mass_storage.c:3383
usb_put_function_instance+0x85/0xa0 drivers/usb/gadget/functions.c:77
fsg_attr_release+0x15/0x20 drivers/usb/gadget/function/f_mass_storage.c:3269
config_item_cleanup fs/configfs/item.c:128 [inline]
config_item_release fs/configfs/item.c:137 [inline]
kref_put include/linux/kref.h:65 [inline]
config_item_put+0x158/0x210 fs/configfs/item.c:149
configfs_rmdir+0x89f/0x960 fs/configfs/dir.c:1540
vfs_rmdir+0x1ae/0x450 fs/namei.c:4157
do_rmdir+0x261/0x6b0 fs/namei.c:4218
__do_sys_rmdir fs/namei.c:4237 [inline]
__se_sys_rmdir fs/namei.c:4235 [inline]
__x64_sys_rmdir+0x49/0x50 fs/namei.c:4235
x64_sys_call+0x25f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:85
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff88810b331c00

which belongs to the cache kmalloc-512 of size 512

The buggy address is located 36 bytes inside of
512-byte region [ffff88810b331c00, ffff88810b331e00)

The buggy address belongs to the page:

page:ffffea00042ccc00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10b330
head:ffffea00042ccc00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea00042cbe00 0000000200000002 ffff888100042f00
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000

page dumped because: kasan: bad access detected
page_owner tracks the page as allocated

page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, ts 3038931514, free_ts 2915566835
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
__alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
alloc_slab_page mm/slub.c:-1 [inline]
allocate_slab mm/slub.c:1937 [inline]
new_slab+0xa0/0x4d0 mm/slub.c:2000
___slab_alloc+0x3ac/0x840 mm/slub.c:3033
__slab_alloc+0x49/0x90 mm/slub.c:3120
slab_alloc_node mm/slub.c:3211 [inline]
slab_alloc mm/slub.c:3255 [inline]
kmem_cache_alloc_trace+0x146/0x270 mm/slub.c:3272
kmalloc include/linux/slab.h:619 [inline]
kzalloc include/linux/slab.h:750 [inline]
dev_pm_qos_constraints_allocate+0x53/0x3f0 drivers/base/power/qos.c:201
__dev_pm_qos_add_request+0x132/0x3e0 drivers/base/power/qos.c:345
dev_pm_qos_add_request+0x37/0x50 drivers/base/power/qos.c:395
usb_hub_create_port_device+0x459/0xad0 drivers/usb/core/port.c:602
hub_configure drivers/usb/core/hub.c:1696 [inline]
hub_probe+0x1f7d/0x2ad0 drivers/usb/core/hub.c:1952
usb_probe_interface+0x60f/0xb20 drivers/usb/core/driver.c:396
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x27d/0x970 drivers/base/dd.c:595
__driver_probe_device+0x193/0x270 drivers/base/dd.c:755
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1474 [inline]
free_pcp_prepare mm/page_alloc.c:1546 [inline]
free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3536
free_unref_page+0xae/0x540 mm/page_alloc.c:3618
free_the_page mm/page_alloc.c:805 [inline]
__free_pages+0x6c/0x100 mm/page_alloc.c:5900
free_pages+0x82/0x90 mm/page_alloc.c:5911
__stack_depot_save+0x453/0x480 lib/stackdepot.c:358
kasan_save_stack mm/kasan/common.c:39 [inline]
kasan_set_track+0x5b/0x70 mm/kasan/common.c:45
kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
____kasan_slab_free+0x125/0x160 mm/kasan/common.c:365
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
kasan_slab_free include/linux/kasan.h:193 [inline]
slab_free_hook mm/slub.c:1728 [inline]
slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
slab_free mm/slub.c:3526 [inline]
kfree+0xc4/0x270 mm/slub.c:4588
kobject_uevent_env+0x343/0x700 lib/kobject_uevent.c:640
kobject_uevent+0x1d/0x30 lib/kobject_uevent.c:657
driver_register+0x3ef/0x440 drivers/base/driver.c:248
usb_register_driver+0x1f7/0x3e0 drivers/usb/core/driver.c:1061
wdm_driver_init+0x1e/0x20 drivers/usb/class/cdc-wdm.c:1375

Memory state around the buggy address:

ffff88810b331b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88810b331b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88810b331c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88810b331c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88810b331d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

==================================================================
------------[ cut here ]------------
refcount_t: underflow; use-after-free.

WARNING: CPU: 0 PID: 345 at lib/refcount.c:28 refcount_warn_saturate+0x120/0x1a0 lib/refcount.c:28
Modules linked in:
CPU: 0 PID: 345 Comm: syz-executor280 Tainted: G B W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026

RIP: 0010:refcount_warn_saturate+0x120/0x1a0 lib/refcount.c:28

Code: 04 01 48 c7 c7 c0 46 63 85 e8 ac 47 5a 02 0f 0b eb c3 e8 43 80 19 ff c6 05 00 ea 95 04 01 48 c7 c7 20 47 63 85 e8 90 47 5a 02 <0f> 0b eb a7 e8 27 80 19 ff c6 05 e1 e9 95 04 01 48 c7 c7 60 46 63
RSP: 0018:ffffc90000c17c38 EFLAGS: 00010246
RAX: dde133087ed16300 RBX: 0000000000000003 RCX: ffff88810bf013c0

RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000

RBP: ffffc90000c17c48 R08: ffff8881f7032f3f R09: 1ffff1103ee065e7
R10: dffffc0000000000 R11: ffffed103ee065e8 R12: 00000000ffffffea

R13: dffffc0000000000 R14: 0000000000000003 R15: 00000000c0000000

FS: 000055558b467480(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 000055558b478858 CR3: 0000000122a2c000 CR4: 00000000003506b0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:

<TASK>

__refcount_sub_and_test include/linux/refcount.h:283 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
kref_put include/linux/kref.h:64 [inline]

config_item_put+0x200/0x210 fs/configfs/item.c:149
configfs_symlink+0x4a6/0x1330 fs/configfs/symlink.c:212
vfs_symlink+0x29e/0x470 fs/namei.c:4437
do_symlinkat+0x24a/0x5d0 fs/namei.c:4466
__do_sys_symlinkat fs/namei.c:4483 [inline]
__se_sys_symlinkat fs/namei.c:4480 [inline]
__x64_sys_symlinkat+0x99/0xb0 fs/namei.c:4480
x64_sys_call+0x74b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:267
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7efd570a5429
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffebd69a858 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00000000000062ce RCX: 00007efd570a5429
RDX: 0000200000000300 RSI: 00000000ffffff9c RDI: 0000200000000200
RBP: 0000000000000000 R08: 00007ffebd69a88c R09: 00007ffebd69a88c
R10: 00007ffebd69a88c R11: 0000000000000246 R12: 00007ffebd69a88c
R13: 00007ffebd69a8c0 R14: 00007ffebd69a8a0 R15: 0000000000000007
</TASK>
---[ end trace 3a037ca40251f3d7 ]---