==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:111 [inline]
BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in kref_get include/linux/kref.h:45 [inline]
BUG: KASAN: use-after-free in config_item_get+0x27/0x90 fs/configfs/item.c:104
Write of size 4 at addr ffff88812d144024 by task syz.3.159/879

CPU: 1 PID: 879 Comm: syz.3.159 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/0x2b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xfe/0x140 mm/kasan/report.c:451
 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_add_relaxed include/linux/atomic/atomic-instrumented.h:111 [inline]
 __refcount_add include/linux/refcount.h:193 [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+0x27/0x90 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+0x44f/0x1330 fs/configfs/symlink.c:191
 vfs_symlink+0x250/0x3e0 fs/namei.c:4480
 do_symlinkat+0x24a/0x5d0 fs/namei.c:4509
 __do_sys_symlinkat fs/namei.c:4526 [inline]
 __se_sys_symlinkat fs/namei.c:4523 [inline]
 __x64_sys_symlinkat+0x99/0xb0 fs/namei.c:4523
 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: 0033:0x7f4f6ac2a019
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:00007f4f6aa8b028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f4f6aeb1fa0 RCX: 00007f4f6ac2a019
RDX: 0000200000000300 RSI: ffffffffffffff9c RDI: 0000200000000200
RBP: 00007f4f6acc100c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4f6aeb2038 R14: 00007f4f6aeb1fa0 R15: 00007ffd8f71d708
 </TASK>

Allocated by task 879:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:513
 __kasan_kmalloc+0xd/0x20 mm/kasan/common.c:522
 kasan_kmalloc include/linux/kasan.h:264 [inline]
 kmem_cache_alloc_trace+0x114/0x220 mm/slub.c:3252
 kmalloc include/linux/slab.h:607 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 fsg_alloc_inst+0x61/0x5a0 drivers/usb/gadget/function/f_mass_storage.c:3335
 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:610
 configfs_mkdir+0x50a/0x9c0 fs/configfs/dir.c:1360
 vfs_mkdir+0x386/0x570 fs/namei.c:4116
 do_mkdirat+0x174/0x4d0 fs/namei.c:4141
 __do_sys_mkdirat fs/namei.c:4156 [inline]
 __se_sys_mkdirat fs/namei.c:4154 [inline]
 __x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4154
 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 867:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:366
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:374
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kfree+0xc0/0x210 mm/slub.c:4564
 fsg_free_inst+0x336/0x420 drivers/usb/gadget/function/f_mass_storage.c:3326
 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:3212
 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:1571
 vfs_rmdir+0x1ae/0x450 fs/namei.c:4200
 do_rmdir+0x261/0x6b0 fs/namei.c:4261
 __do_sys_rmdir fs/namei.c:4280 [inline]
 __se_sys_rmdir fs/namei.c:4278 [inline]
 __x64_sys_rmdir+0x49/0x50 fs/namei.c:4278
 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 ffff88812d144000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 36 bytes inside of
 512-byte region [ffff88812d144000, ffff88812d144200)
The buggy address belongs to the page:
page:ffffea0004b45100 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12d144
head:ffffea0004b45100 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea000445fa00 0000000500000005 ffff888100041c80
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 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 0, ts 26106026335, free_ts 25874493749
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x132/0x160 mm/page_alloc.c:2420
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x2eb1/0x2f80 mm/page_alloc.c:4192
 __alloc_pages+0x242/0x4f0 mm/page_alloc.c:5501
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0x98/0x460 mm/slub.c:1980
 ___slab_alloc+0x3ac/0x840 mm/slub.c:3013
 __slab_alloc+0x49/0x90 mm/slub.c:3100
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 __kmalloc_track_caller+0x165/0x270 mm/slub.c:4930
 kmalloc_reserve net/core/skbuff.c:356 [inline]
 __alloc_skb+0x210/0x730 net/core/skbuff.c:427
 __napi_alloc_skb+0x162/0x2e0 net/core/skbuff.c:568
 napi_alloc_skb include/linux/skbuff.h:3081 [inline]
 page_to_skb+0x274/0xb60 drivers/net/virtio_net.c:474
 receive_mergeable drivers/net/virtio_net.c:1102 [inline]
 receive_buf+0xce9/0x4c60 drivers/net/virtio_net.c:1212
 virtnet_receive drivers/net/virtio_net.c:1504 [inline]
 virtnet_poll+0x5ce/0xfb0 drivers/net/virtio_net.c:1620
 __napi_poll+0xbb/0x580 net/core/dev.c:7101
 napi_poll net/core/dev.c:7168 [inline]
 net_rx_action+0x37f/0x910 net/core/dev.c:7258
 handle_softirqs+0x225/0x530 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0xc3/0x190 kernel/softirq.c:659
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1413 [inline]
 free_unref_page_prepare+0x4f6/0x530 mm/page_alloc.c:3317
 free_unref_page+0x7d/0x1e0 mm/page_alloc.c:3396
 __put_single_page mm/swap.c:98 [inline]
 __put_page+0xad/0xe0 mm/swap.c:129
 put_page include/linux/mm.h:1258 [inline]
 anon_pipe_buf_release+0x15c/0x1d0 fs/pipe.c:137
 pipe_buf_release include/linux/pipe_fs_i.h:219 [inline]
 pipe_read+0x563/0x1050 fs/pipe.c:323
 call_read_iter include/linux/fs.h:2167 [inline]
 new_sync_read fs/read_write.c:404 [inline]
 vfs_read+0x6c0/0xc20 fs/read_write.c:485
 ksys_read+0x14a/0x260 fs/read_write.c:623
 __do_sys_read fs/read_write.c:633 [inline]
 __se_sys_read fs/read_write.c:631 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:631
 x64_sys_call+0x96d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
 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

Memory state around the buggy address:
 ffff88812d143f00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88812d143f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88812d144000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff88812d144080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88812d144100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
refcount_t: saturated; leaking memory.
WARNING: CPU: 1 PID: 879 at lib/refcount.c:22 refcount_warn_saturate+0x158/0x1a0 lib/refcount.c:22
Modules linked in:
CPU: 1 PID: 879 Comm: syz.3.159 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+0x158/0x1a0 lib/refcount.c:22
Code: 04 01 48 c7 c7 c0 21 42 85 e8 74 42 45 02 0f 0b eb 8b e8 db a9 25 ff c6 05 1c bb 7f 04 01 48 c7 c7 c0 21 42 85 e8 58 42 45 02 <0f> 0b e9 6c ff ff ff e8 bc a9 25 ff c6 05 01 bb 7f 04 01 48 c7 c7
RSP: 0018:ffffc900019c7c58 EFLAGS: 00010246
RAX: 50572f58f2c55e00 RBX: 0000000000000001 RCX: ffff888102ba6600
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900019c7c68 R08: ffffc900019c7687 R09: fffff52000338f00
R10: dffffc0000000000 R11: fffff52000338ed1 R12: ffff88811fea94e0
R13: dffffc0000000000 R14: 0000000000000001 R15: 00000000c0000000
FS:  00007f4f6aa8b6c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8fdd804d58 CR3: 0000000122622000 CR4: 00000000003506a0
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+0x8c/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+0x44f/0x1330 fs/configfs/symlink.c:191
 vfs_symlink+0x250/0x3e0 fs/namei.c:4480
 do_symlinkat+0x24a/0x5d0 fs/namei.c:4509
 __do_sys_symlinkat fs/namei.c:4526 [inline]
 __se_sys_symlinkat fs/namei.c:4523 [inline]
 __x64_sys_symlinkat+0x99/0xb0 fs/namei.c:4523
 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: 0033:0x7f4f6ac2a019
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:00007f4f6aa8b028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f4f6aeb1fa0 RCX: 00007f4f6ac2a019
RDX: 0000200000000300 RSI: ffffffffffffff9c RDI: 0000200000000200
RBP: 00007f4f6acc100c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4f6aeb2038 R14: 00007f4f6aeb1fa0 R15: 00007ffd8f71d708
 </TASK>
---[ end trace 244ba7c8af0c1870 ]---