KASAN: use-after-free Write in gadgetfs_kill_sb

Status: upstream: reported on 2026/09/01 15:24
Reported-by: syzbot+261bf9307ccfe695419e@syzkaller.appspotmail.com
First crash: 5d10h, last: 5d10h
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Write in gadgetfs_kill_sb usb 22 syz, C error 5 1329d 1363d 22/29 fixed on 2023/06/08 14:41
upstream KASAN: slab-use-after-free Write in gadgetfs_kill_sb prio:normal actionable usb 22 C 5 2d18h 33d 0/29 upstream: reported C repro on 2026/08/04 02:08

Sample crash report:
==================================================================
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 put_dev drivers/usb/gadget/legacy/inode.c:159 [inline]
BUG: KASAN: use-after-free in gadgetfs_kill_sb+0x3f/0x100 drivers/usb/gadget/legacy/inode.c:2102
Write of size 4 at addr ffff88802b951040 by task syz.9.1315/9775

CPU: 0 PID: 9775 Comm: syz.9.1315 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x235/0x290 mm/kasan/generic.c:189
 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]
 put_dev drivers/usb/gadget/legacy/inode.c:159 [inline]
 gadgetfs_kill_sb+0x3f/0x100 drivers/usb/gadget/legacy/inode.c:2102
 deactivate_locked_super+0x93/0xf0 fs/super.c:335
 cleanup_mnt+0x426/0x4d0 fs/namespace.c:1148
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f8eefed7159
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:00007f8eee10e028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f8ef015f090 RCX: 00007f8eefed7159
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000200000000040
RBP: 00007f8eeff6e024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8ef015f128 R14: 00007f8ef015f090 R15: 00007ffc8940da98
 </TASK>

Allocated by task 9689:
 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 mm/kasan/common.c:513 [inline]
 __kasan_kmalloc+0xaf/0xe0 mm/kasan/common.c:522
 kmalloc_reserve net/core/skbuff.c:356 [inline]
 __alloc_skb+0x22c/0x750 net/core/skbuff.c:427
 alloc_skb include/linux/skbuff.h:1162 [inline]
 __tcp_send_ack+0x9d/0x5d0 net/ipv4/tcp_output.c:3996
 tcp_rcv_synsent_state_process net/ipv4/tcp_input.c:6372 [inline]
 tcp_rcv_state_process+0x2d51/0x41e0 net/ipv4/tcp_input.c:6542
 tcp_v4_do_rcv+0x666/0x9b0 net/ipv4/tcp_ipv4.c:1754
 sk_backlog_rcv include/net/sock.h:1080 [inline]
 __release_sock+0x1e6/0x460 net/core/sock.c:2730
 release_sock+0x5b/0x1b0 net/core/sock.c:3273
 inet_wait_for_connect net/ipv4/af_inet.c:604 [inline]
 __inet_stream_connect+0x6be/0xd80 net/ipv4/af_inet.c:697
 inet_stream_connect+0x62/0xa0 net/ipv4/af_inet.c:736
 mptcp_stream_connect+0x5b5/0x850 net/mptcp/protocol.c:3488
 __sys_connect_file net/socket.c:1933 [inline]
 __sys_connect+0x3cb/0x450 net/socket.c:1950
 __do_sys_connect net/socket.c:1960 [inline]
 __se_sys_connect net/socket.c:1957 [inline]
 __x64_sys_connect+0x76/0x80 net/socket.c:1957
 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 9648:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xec/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kfree+0xef/0x2a0 mm/slub.c:4564
 skb_free_head net/core/skbuff.c:655 [inline]
 skb_release_data+0x667/0x830 net/core/skbuff.c:677
 skb_release_all net/core/skbuff.c:742 [inline]
 __kfree_skb net/core/skbuff.c:756 [inline]
 kfree_skb_reason+0xaf/0x110 net/core/skbuff.c:776
 tcp_v4_rcv+0x327/0x2da0 net/ipv4/tcp_ipv4.c:2180
 ip_protocol_deliver_rcu+0x38c/0x740 net/ipv4/ip_input.c:204
 ip_local_deliver_finish+0x1d8/0x320 net/ipv4/ip_input.c:231
 NF_HOOK+0x303/0x390 include/linux/netfilter.h:302
 NF_HOOK+0x303/0x390 include/linux/netfilter.h:302
 __netif_receive_skb_one_core net/core/dev.c:5551 [inline]
 __netif_receive_skb+0xcc/0x290 net/core/dev.c:5665
 process_backlog+0x366/0x770 net/core/dev.c:6542
 __napi_poll+0xbb/0x430 net/core/dev.c:7101
 napi_poll net/core/dev.c:7168 [inline]
 net_rx_action+0x522/0xa80 net/core/dev.c:7258
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676

The buggy address belongs to the object at ffff88802b951000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 64 bytes inside of
 1024-byte region [ffff88802b951000, ffff88802b951400)
The buggy address belongs to the page:
page:ffffea0000ae5400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2b950
head:ffffea0000ae5400 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888016c41dc0
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x52a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 154, ts 71006670523, free_ts 70926232195
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x807/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 __kmalloc+0x11d/0x340 mm/slub.c:4408
 kmalloc include/linux/slab.h:612 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 ieee802_11_parse_elems_crc+0xb3/0x1090 net/mac80211/util.c:1478
 ieee802_11_parse_elems net/mac80211/ieee80211_i.h:2243 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1609 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x36b/0x2b50 net/mac80211/ibss.c:1643
 ieee80211_iface_process_skb net/mac80211/iface.c:1465 [inline]
 ieee80211_iface_work+0x714/0xc50 net/mac80211/iface.c:1519
 cfg80211_wiphy_work+0x224/0x260 net/wireless/core.c:433
 process_one_work+0x867/0xff0 kernel/workqueue.c:2310
 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
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:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
 qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xc0 mm/kasan/common.c:444
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3225 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x15d/0x280 mm/slub.c:3238
 sock_alloc_inode+0x17/0xb0 net/socket.c:305
 alloc_inode fs/inode.c:261 [inline]
 new_inode_pseudo+0x5f/0x210 fs/inode.c:1001
 sock_alloc net/socket.c:628 [inline]
 __sock_create+0x128/0x910 net/socket.c:1460
 sock_create net/socket.c:1552 [inline]
 __sys_socket+0xe2/0x170 net/socket.c:1594
 __do_sys_socket net/socket.c:1603 [inline]
 __se_sys_socket net/socket.c:1601 [inline]
 __x64_sys_socket+0x76/0x80 net/socket.c:1601
 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:
 ffff88802b950f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802b950f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802b951000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff88802b951080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802b951100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/01 15:24 linux-5.15.y 28c35638ec51 587f6b29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Write in gadgetfs_kill_sb
* Struck through repros no longer work on HEAD.