KASAN: use-after-free Read in vhci_cleanup_unlink_list

Status: upstream: reported C repro on 2026/07/31 00:36
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+fb0dfa359acaa55afdb7@syzkaller.appspotmail.com
First crash: 90d, last: 67d
Fix bisection: failed (error log)
  
▶ ▼ Bug presence (3)
Date Name Commit Repro Result
2026/10/24 linux-6.1.y (ToT) 79807e970724 C [report] KASAN: use-after-free Read in vhci_shutdown_connection
2026/08/21 upstream (ToT) 818bebeb63dd C [report] KASAN: slab-use-after-free Read in vhci_shutdown_connection
2026/10/24 upstream (ToT) 5b0764a53235 C Didn't crash
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 KASAN: use-after-free Read in vhci_cleanup_unlink_list origin:lts-only 19 syz, C error 10 70d 92d 0/3 upstream: reported C repro on 2026/07/29 00:21
linux-6.6 KASAN: slab-use-after-free Read in vhci_cleanup_unlink_list 19 2 77d 80d 0/2 upstream: reported on 2026/08/10 07:01
upstream KASAN: slab-use-after-free Read in vhci_cleanup_unlink_list prio:normal usb 19 syz, C error 257 63d 89d 0/29 closed as invalid on 2026/09/08 09:20

Sample crash report:
vhci_hcd: release socket
==================================================================
BUG: KASAN: use-after-free in vdev_to_vhci_hcd drivers/usb/usbip/vhci.h:171 [inline]
BUG: KASAN: use-after-free in vhci_cleanup_unlink_list+0x3a8/0x3ac drivers/usb/usbip/vhci_hcd.c:981
Read of size 4 at addr ffff0000d25e4670 by task kworker/u4:2/39

CPU: 1 PID: 39 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
Workqueue: usbip_event event_handler
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 __asan_report_load4_noabort+0x2c/0x38 mm/kasan/report_generic.c:350
 vdev_to_vhci_hcd drivers/usb/usbip/vhci.h:171 [inline]
 vhci_cleanup_unlink_list+0x3a8/0x3ac drivers/usb/usbip/vhci_hcd.c:981
 vhci_device_unlink_cleanup drivers/usb/usbip/vhci_hcd.c:1024 [inline]
 vhci_shutdown_connection+0x28c/0x574 drivers/usb/usbip/vhci_hcd.c:1064
 event_handler+0x288/0x454 drivers/usb/usbip/usbip_event.c:79
 process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292
 worker_thread+0x8cc/0xfe8 kernel/workqueue.c:2439
 kthread+0x254/0x2e0 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Allocated by task 1:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
 kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 __do_kmalloc_node mm/slab_common.c:936 [inline]
 __kmalloc+0xd8/0x180 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 __usb_create_hcd+0x6c/0x740 drivers/usb/core/hcd.c:2581
 usb_create_shared_hcd+0x40/0x54 drivers/usb/core/hcd.c:2657
 vhci_hcd_probe+0x1a4/0x354 drivers/usb/usbip/vhci_hcd.c:1393
 platform_probe+0x148/0x1c8 drivers/base/platform.c:1400
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x3a0/0xac4 drivers/base/dd.c:638
 __driver_probe_device+0x1c8/0x368 drivers/base/dd.c:804
 driver_probe_device+0x78/0x324 drivers/base/dd.c:834
 __device_attach_driver+0x28c/0x4c0 drivers/base/dd.c:962
 bus_for_each_drv+0x154/0x1e4 drivers/base/bus.c:429
 __device_attach+0x2a4/0x3d8 drivers/base/dd.c:1034
 device_initial_probe+0x24/0x34 drivers/base/dd.c:1083
 bus_probe_device+0xbc/0x1c4 drivers/base/bus.c:489
 device_add+0x93c/0xe4c drivers/base/core.c:3712
 platform_device_add+0x3f8/0x6f4 drivers/base/platform.c:717
 vhci_hcd_init+0x390/0x4b0 drivers/usb/usbip/vhci_hcd.c:1571
 do_one_initcall+0x278/0x9f0 init/main.c:1309
 do_initcall_level+0x158/0x214 init/main.c:1382
 do_initcalls+0x58/0xac init/main.c:1398
 do_basic_setup+0x8c/0xa0 init/main.c:1417
 kernel_init_freeable+0x35c/0x4f0 init/main.c:1637
 kernel_init+0x24/0x1d8 init/main.c:1525
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Freed by task 4463:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
 kasan_save_free_info+0x38/0x5c mm/kasan/generic.c:516
 ____kasan_slab_free+0x148/0x1b0 mm/kasan/common.c:237
 __kasan_slab_free+0x18/0x28 mm/kasan/common.c:245
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x16c/0x1e8 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 __kmem_cache_free+0xbc/0x21c mm/slub.c:3700
 kfree+0xd0/0x1a8 mm/slab_common.c:988
 hcd_release drivers/usb/core/hcd.c:2707 [inline]
 kref_put include/linux/kref.h:65 [inline]
 usb_put_hcd+0x124/0x16c drivers/usb/core/hcd.c:2721
 vhci_hcd_remove+0x98/0x100 drivers/usb/usbip/vhci_hcd.c:1431
 platform_remove+0x98/0xf0 drivers/base/platform.c:1422
 device_remove drivers/base/dd.c:547 [inline]
 __device_release_driver drivers/base/dd.c:1279 [inline]
 device_release_driver_internal+0x3d4/0x6e4 drivers/base/dd.c:1305
 device_driver_detach+0x48/0x58 drivers/base/dd.c:1341
 unbind_store+0x2a8/0x2b4 drivers/base/bus.c:193
 drv_attr_store+0x80/0xa4 drivers/base/bus.c:77
 sysfs_kf_write+0x1f8/0x274 fs/sysfs/file.c:140
 kernfs_fop_write_iter+0x390/0x4b4 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x3c8/0x7c8 fs/read_write.c:584
 ksys_write+0x12c/0x228 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:646
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the object at ffff0000d25e4000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 1648 bytes inside of
 8192-byte region [ffff0000d25e4000, ffff0000d25e6000)

The buggy address belongs to the physical page:
page:00000000fef2e3bb refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1125e0
head:00000000fef2e3bb order:3 compound_mapcount:0 compound_pincount:0
flags: 0x5ffc00000010200(slab|head|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000010200 0000000000000000 dead000000000122 ffff0000c0002c00
raw: 0000000000000000 0000000000020002 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000d25e4500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000d25e4580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff0000d25e4600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                             ^
 ffff0000d25e4680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000d25e4700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/02 05:01 linux-6.1.y fb28aa725e05 e611ffe1 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/08/02 01:58 linux-6.1.y fb28aa725e05 e611ffe1 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/08/18 09:21 linux-6.1.y e4f7d8be268e 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/08/17 23:11 linux-6.1.y e4f7d8be268e 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/08/17 21:18 linux-6.1.y e4f7d8be268e 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/08/13 02:12 linux-6.1.y e4f7d8be268e 359b2492 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/08/10 15:47 linux-6.1.y e4f7d8be268e 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/08/10 09:43 linux-6.1.y e4f7d8be268e 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/07/31 00:35 linux-6.1.y fb28aa725e05 aaffb173 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/08/23 05:31 linux-6.1.y 7e6e67054721 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/08/08 23:11 linux-6.1.y e4f7d8be268e 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in vhci_cleanup_unlink_list
2026/08/01 23:40 linux-6.1.y fb28aa725e05 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in vhci_cleanup_unlink_list
* Struck through repros no longer work on HEAD.