[moderation] [usb?] KASAN: slab-use-after-free Write in gadgetfs_kill_sb

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 11028ab62899 Merge tag 'probes-fixes-v7.2-rc5' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15b8b561580000
kernel config: https://syzkaller.appspot.com/x/.config?x=cb17729fb04b1e3a
dashboard link: https://syzkaller.appspot.com/bug?extid=5d1d4d6e7b22d89462c1
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
CC: [gre...@linuxfoundation.org linux-...@vger.kernel.org linu...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0afad3dd27f4/disk-11028ab6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2e1441f9c31d/vmlinux-11028ab6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5f0b8bdf00cd/bzImage-11028ab6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5d1d4d...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:112 [inline]
BUG: KASAN: slab-use-after-free in atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline]
BUG: KASAN: slab-use-after-free in __refcount_sub_and_test include/linux/refcount.h:389 [inline]
BUG: KASAN: slab-use-after-free in __refcount_dec_and_test include/linux/refcount.h:432 [inline]
BUG: KASAN: slab-use-after-free in refcount_dec_and_test include/linux/refcount.h:450 [inline]
BUG: KASAN: slab-use-after-free in put_dev drivers/usb/gadget/legacy/inode.c:165 [inline]
BUG: KASAN: slab-use-after-free in gadgetfs_kill_sb+0x46/0x110 drivers/usb/gadget/legacy/inode.c:2104
Write of size 4 at addr ffff88803bfae880 by task syz-executor/5596

CPU: 1 UID: 0 PID: 5596 Comm: syz-executor Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
instrument_atomic_read_write include/linux/instrumented.h:112 [inline]
atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline]
__refcount_sub_and_test include/linux/refcount.h:389 [inline]
__refcount_dec_and_test include/linux/refcount.h:432 [inline]
refcount_dec_and_test include/linux/refcount.h:450 [inline]
put_dev drivers/usb/gadget/legacy/inode.c:165 [inline]
gadgetfs_kill_sb+0x46/0x110 drivers/usb/gadget/legacy/inode.c:2104
deactivate_locked_super+0xbc/0x130 fs/super.c:477
cleanup_mnt+0x3d3/0x460 fs/namespace.c:1317
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x221a/0x2240 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbce50adf99
Code: Unable to access opcode bytes at 0x7fbce50adf6f.
RSP: 002b:00007ffcd063bfe8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fbce50adf99
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000043
RBP: 00007fbce5145dfc R08: 0000000000000000 R09: 00000000000927c0
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000001c
R13: 00000000000927c0 R14: 0000000000028fe2 R15: 00007ffcd063c1a0
</TASK>

Allocated by task 1029:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5334 [inline]
__kmalloc_node_track_caller_noprof+0x57f/0x7c0 mm/slub.c:5471
kmalloc_reserve net/core/skbuff.c:637 [inline]
pskb_expand_head+0x22c/0x13a0 net/core/skbuff.c:2306
__skb_cow include/linux/skbuff.h:3880 [inline]
skb_cow_head include/linux/skbuff.h:3914 [inline]
batadv_skb_head_push+0x169/0x200 net/batman-adv/mesh-interface.c:73
batadv_send_skb_packet+0xc8/0x650 net/batman-adv/send.c:81
batadv_iv_ogm_send_to_if net/batman-adv/bat_iv_ogm.c:400 [inline]
batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:428 [inline]
batadv_iv_send_outstanding_bat_ogm_packet+0x5e8/0x790 net/batman-adv/bat_iv_ogm.c:1795
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 1029:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2677 [inline]
slab_free mm/slub.c:6377 [inline]
kfree+0x1c5/0x6c0 mm/slub.c:6692
skb_kfree_head net/core/skbuff.c:1077 [inline]
skb_free_head net/core/skbuff.c:1089 [inline]
skb_release_data+0x85e/0xab0 net/core/skbuff.c:1116
skb_release_all net/core/skbuff.c:1191 [inline]
__kfree_skb+0x5d/0x210 net/core/skbuff.c:1205
kfree_skb_reason include/linux/skbuff.h:1323 [inline]
__netif_receive_skb_core+0x2b5c/0x30b0 net/core/dev.c:6186
__netif_receive_skb_one_core net/core/dev.c:6210 [inline]
__netif_receive_skb net/core/dev.c:6325 [inline]
process_backlog+0x351/0xc50 net/core/dev.c:6676
__napi_poll+0xae/0x550 net/core/dev.c:7735
napi_poll net/core/dev.c:7798 [inline]
net_rx_action+0x621/0xd70 net/core/dev.c:7955
handle_softirqs+0x1d9/0x6c0 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
__local_bh_enable_ip+0x170/0x2b0 kernel/softirq.c:302
local_bh_enable include/linux/bottom_half.h:33 [inline]
rcu_read_unlock_bh include/linux/rcupdate.h:914 [inline]
__dev_queue_xmit+0x1ee9/0x3880 net/core/dev.c:4913
dev_queue_xmit include/linux/netdevice.h:3446 [inline]
batadv_send_skb_packet+0x400/0x650 net/batman-adv/send.c:100
batadv_iv_ogm_send_to_if net/batman-adv/bat_iv_ogm.c:400 [inline]
batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:428 [inline]
batadv_iv_send_outstanding_bat_ogm_packet+0x5e8/0x790 net/batman-adv/bat_iv_ogm.c:1795
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff88803bfae800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 128 bytes inside of
freed 1024-byte region [ffff88803bfae800, ffff88803bfaec00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3bfa8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813ffb1dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88813ffb1dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 0080000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5381, tgid 5381 (dhcpcd-run-hook), ts 55321250949, free_ts 55230640080
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
prep_new_page mm/page_alloc.c:1867 [inline]
get_page_from_freelist+0x262a/0x26a0 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
alloc_slab_page mm/slub.c:3266 [inline]
allocate_slab+0x79/0x5e0 mm/slub.c:3380
new_slab mm/slub.c:3426 [inline]
refill_objects+0x2d8/0x350 mm/slub.c:7310
refill_sheaf mm/slub.c:2804 [inline]
__pcs_replace_empty_main+0x330/0x690 mm/slub.c:4675
alloc_from_pcs mm/slub.c:4773 [inline]
slab_alloc_node mm/slub.c:4905 [inline]
__do_kmalloc_node mm/slub.c:5333 [inline]
__kmalloc_noprof+0x544/0x780 mm/slub.c:5359
_kmalloc_noprof include/linux/slab.h:992 [inline]
load_elf_phdrs+0x13e/0x240 fs/binfmt_elf.c:540
load_elf_binary+0xa2f/0x2970 fs/binfmt_elf.c:969
search_binary_handler fs/exec.c:1694 [inline]
exec_binprm fs/exec.c:1726 [inline]
bprm_execve+0x926/0x14b0 fs/exec.c:1778
do_execveat_common+0x4f4/0x670 fs/exec.c:1876
__do_sys_execve fs/exec.c:1949 [inline]
__se_sys_execve fs/exec.c:1943 [inline]
__x64_sys_execve+0x97/0xc0 fs/exec.c:1943
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5377 tgid 5377 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1406 [inline]
__free_frozen_pages+0x10e7/0x11c0 mm/page_alloc.c:2950
__slab_free+0x252/0x2a0 mm/slub.c:5741
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4584 [inline]
slab_alloc_node mm/slub.c:4917 [inline]
kmem_cache_alloc_noprof+0x355/0x650 mm/slub.c:4931
alloc_filename fs/namei.c:147 [inline]
do_getname+0x2e/0x250 fs/namei.c:187
class_filename_flags_constructor include/linux/fs.h:2566 [inline]
do_sys_openat2+0xcc/0x200 fs/open.c:1367
do_sys_open fs/open.c:1374 [inline]
__do_sys_openat fs/open.c:1390 [inline]
__se_sys_openat fs/open.c:1385 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1385
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff88803bfae780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88803bfae800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88803bfae880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88803bfae900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88803bfae980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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