syzbot
KASAN: slab-use-after-free Read in dummy_timer
Status:
upstream: reported on 2026/08/22 02:22
Subsystems:
usb
Labels:
prio:normal
[Documentation on labels]
Reported-by: syzbot+ba7702afee9d7d1375f0@syzkaller.appspotmail.com
First crash: 8d15h, last: 1d04h
Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in find_endpoint drivers/usb/gadget/udc/dummy_hcd.c:1618 [inline]
BUG: KASAN: slab-use-after-free in dummy_timer+0xcdb/0x4cf0 drivers/usb/gadget/udc/dummy_hcd.c:1890
Read of size 1 at addr ffff8880279f9127 by task syz.0.380/6887
CPU: 0 UID: 0 PID: 6887 Comm: syz.0.380 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
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
find_endpoint drivers/usb/gadget/udc/dummy_hcd.c:1618 [inline]
dummy_timer+0xcdb/0x4cf0 drivers/usb/gadget/udc/dummy_hcd.c:1890
__run_hrtimer kernel/time/hrtimer.c:2068 [inline]
__hrtimer_run_queues+0x3bc/0xa10 kernel/time/hrtimer.c:2125
hrtimer_run_softirq+0x1e3/0x2e0 kernel/time/hrtimer.c:2142
handle_softirqs+0x226/0x860 kernel/softirq.c:645
__do_softirq kernel/softirq.c:679 [inline]
invoke_softirq kernel/softirq.c:519 [inline]
__irq_exit_rcu+0xcb/0x220 kernel/softirq.c:767
irq_exit_rcu+0x9/0x30 kernel/softirq.c:784
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:211 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x47/0x80 kernel/locking/spinlock.c:221
Code: f7 e8 5d 6a b3 f5 f7 c3 00 02 00 00 74 05 e8 c0 a2 df f5 9c 58 a9 00 02 00 00 75 29 f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 14 86 a4 f5 65 48 8b 05 bc ce c8 07 48 85 c0 74 18 5b 41 5e e9
RSP: 0018:ffffc9000398fd08 EFLAGS: 00000206
RAX: 0000000000000006 RBX: 0000000000000282 RCX: 8000000000000001
RDX: 0000000000000006 RSI: ffffffff8e586ce4 RDI: 0000000000000001
RBP: ffffc9000398fea8 R08: ffffffff909ba57f R09: 1ffffffff21374af
R10: dffffc0000000000 R11: fffffbfff21374b0 R12: dffffc0000000000
R13: 1ffff92000731fac R14: ffff888069752910 R15: ffffc9000398fda0
hiddev_ioctl+0x1097/0x16f0 drivers/hid/usbhid/hiddev.c:726
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f32ba19e0d9
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:00007f32bafd6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f32ba425fa0 RCX: 00007f32ba19e0d9
RDX: 0000200000000400 RSI: 00000000400c4808 RDI: 0000000000000008
RBP: 00007f32ba235024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f32ba426038 R14: 00007f32ba425fa0 R15: 00007ffdf6daec98
</TASK>
Allocated by task 6607:
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:5414 [inline]
__kmalloc_noprof+0x36b/0x720 mm/slub.c:5439
_kmalloc_noprof include/linux/slab.h:995 [inline]
usb_copy_descriptors+0xf7/0x320 drivers/usb/gadget/config.c:82
f_midi2_bind+0x2736/0x2c40 drivers/usb/gadget/function/f_midi2.c:2026
usb_add_function+0x2e1/0x9f0 drivers/usb/gadget/composite.c:333
configfs_composite_bind+0xde0/0x1410 drivers/usb/gadget/configfs.c:1802
gadget_bind_driver+0x2ca/0x9e0 drivers/usb/gadget/udc/core.c:1662
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x254/0xae0 drivers/base/dd.c:706
__driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
__driver_attach+0x339/0x600 drivers/base/dd.c:1292
bus_for_each_dev+0x23b/0x2c0 drivers/base/bus.c:383
bus_add_driver+0x345/0x670 drivers/base/bus.c:763
driver_register+0x23a/0x320 drivers/base/driver.c:174
usb_gadget_register_driver_owner+0xf9/0x270 drivers/usb/gadget/udc/core.c:1752
gadget_dev_desc_UDC_store+0x1c9/0x2f0 drivers/usb/gadget/configfs.c:300
flush_write_buffer fs/configfs/file.c:207 [inline]
configfs_write_iter+0x337/0x430 fs/configfs/file.c:229
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x612/0xba0 fs/read_write.c:687
ksys_write+0x150/0x270 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 6759:
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:2748 [inline]
slab_free mm/slub.c:6499 [inline]
kfree+0x1c5/0x650 mm/slub.c:6792
usb_free_descriptors include/linux/usb/gadget.h:903 [inline]
usb_free_all_descriptors+0x78/0x110 drivers/usb/gadget/config.c:151
purge_configs_funcs+0x248/0x3d0 drivers/usb/gadget/configfs.c:1600
configfs_composite_unbind+0xa4/0x1c0 drivers/usb/gadget/configfs.c:1846
gadget_unbind_driver+0x1cb/0x410 drivers/usb/gadget/udc/core.c:1724
device_remove drivers/base/dd.c:616 [inline]
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x48b/0x880 drivers/base/dd.c:1372
driver_detach+0x1f3/0x2d0 drivers/base/dd.c:1435
bus_remove_driver+0x226/0x320 drivers/base/bus.c:832
usb_gadget_unregister_driver+0x4e/0x70 drivers/usb/gadget/udc/core.c:1784
unregister_gadget drivers/usb/gadget/configfs.c:263 [inline]
gadget_dev_desc_UDC_store+0x17a/0x2f0 drivers/usb/gadget/configfs.c:290
flush_write_buffer fs/configfs/file.c:207 [inline]
configfs_write_iter+0x337/0x430 fs/configfs/file.c:229
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x612/0xba0 fs/read_write.c:687
ksys_write+0x150/0x270 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff8880279f9000
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 295 bytes inside of
freed 512-byte region [ffff8880279f9000, ffff8880279f9200)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x279f8
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88813ff15c80 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813ff15c80 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000002 ffffffffffffff01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
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 5615, tgid 5615 (syz-executor), ts 90656481770
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1871
prep_new_page mm/page_alloc.c:1879 [inline]
get_page_from_freelist+0x2209/0x2280 mm/page_alloc.c:3943
__alloc_frozen_pages_noprof+0x217/0x5a0 mm/page_alloc.c:5436
alloc_slab_page mm/slub.c:3347 [inline]
allocate_slab+0x7d/0x620 mm/slub.c:3462
new_slab mm/slub.c:3513 [inline]
refill_objects+0x2d5/0x350 mm/slub.c:7410
refill_sheaf mm/slub.c:2885 [inline]
__pcs_replace_empty_main+0x2c8/0x6c0 mm/slub.c:4774
alloc_from_pcs mm/slub.c:4850 [inline]
slab_alloc_node mm/slub.c:4984 [inline]
__do_kmalloc_node mm/slub.c:5413 [inline]
__kmalloc_noprof+0x47b/0x720 mm/slub.c:5439
_kmalloc_noprof include/linux/slab.h:995 [inline]
_kzalloc_noprof include/linux/slab.h:1312 [inline]
fib6_info_alloc+0x30/0xf0 net/ipv6/ip6_fib.c:155
ip6_route_info_create+0x149/0x890 net/ipv6/route.c:3833
ip6_route_add+0x49/0x1b0 net/ipv6/route.c:3962
addrconf_add_mroute+0x2d1/0x370 net/ipv6/addrconf.c:2568
addrconf_add_dev net/ipv6/addrconf.c:2586 [inline]
inet6_addr_add+0x2b8/0xb50 net/ipv6/addrconf.c:3056
inet6_rtm_newaddr+0x9fc/0xe00 net/ipv6/addrconf.c:5095
rtnetlink_rcv_msg+0x802/0xc00 net/core/rtnetlink.c:7132
netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1345
page last free pid 5327 tgid 5327 ts 55156601657 stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
__free_pages_prepare mm/page_alloc.c:1418 [inline]
__free_frozen_pages+0xc93/0xd90 mm/page_alloc.c:2962
__slab_free+0x274/0x2c0 mm/slub.c:5815
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:4683 [inline]
slab_alloc_node mm/slub.c:4996 [inline]
__do_kmalloc_node mm/slub.c:5413 [inline]
__kmalloc_noprof+0x307/0x720 mm/slub.c:5439
_kmalloc_noprof include/linux/slab.h:995 [inline]
tomoyo_realpath_from_path+0xef/0x640 security/tomoyo/realpath.c:251
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x283/0x560 security/tomoyo/file.c:827
security_inode_getattr+0x12b/0x310 security/security.c:1895
vfs_getattr fs/stat.c:259 [inline]
vfs_fstat fs/stat.c:281 [inline]
__do_sys_newfstat fs/stat.c:551 [inline]
__se_sys_newfstat fs/stat.c:546 [inline]
__x64_sys_newfstat+0x133/0x270 fs/stat.c:546
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Memory state around the buggy address:
ffff8880279f9000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880279f9080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880279f9100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880279f9180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880279f9200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: f7 e8 imul %eax
2: 5d pop %rbp
3: 6a b3 push $0xffffffffffffffb3
5: f5 cmc
6: f7 c3 00 02 00 00 test $0x200,%ebx
c: 74 05 je 0x13
e: e8 c0 a2 df f5 call 0xf5dfa2d3
13: 9c pushf
14: 58 pop %rax
15: a9 00 02 00 00 test $0x200,%eax
1a: 75 29 jne 0x45
1c: f7 c3 00 02 00 00 test $0x200,%ebx
22: 74 01 je 0x25
24: fb sti
25: bf 01 00 00 00 mov $0x1,%edi
* 2a: e8 14 86 a4 f5 call 0xf5a48643 <-- trapping instruction
2f: 65 48 8b 05 bc ce c8 mov %gs:0x7c8cebc(%rip),%rax # 0x7c8cef3
36: 07
37: 48 85 c0 test %rax,%rax
3a: 74 18 je 0x54
3c: 5b pop %rbx
3d: 41 5e pop %r14
3f: e9 .byte 0xe9
Struck through repros no longer work on HEAD.