[moderation] [usb?] KASAN: slab-use-after-free Read in vhci_tx_loop

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ea1013c15392 Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17d0977c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1f2b6fe1fdf1a00b
dashboard link: https://syzkaller.appspot.com/bug?extid=191e53e581803f484403
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [gre...@linuxfoundation.org i...@zenithal.me linux-...@vger.kernel.org linu...@vger.kernel.org sh...@kernel.org valentin...@gmail.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/dd818bf7bc64/disk-ea1013c1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/711f86610a41/vmlinux-ea1013c1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/023de520c887/bzImage-ea1013c1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+191e53...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in vhci_send_cmd_submit drivers/usb/usbip/vhci_tx.c:69 [inline]
BUG: KASAN: slab-use-after-free in vhci_tx_loop+0x38e/0x1a80 drivers/usb/usbip/vhci_tx.c:241
Read of size 8 at addr ffff888033c85fa0 by task vhci_tx/11778

CPU: 0 UID: 0 PID: 11778 Comm: vhci_tx Tainted: G L syzkaller #0 PREEMPT_{RT,(full)}
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xca/0x240 mm/kasan/report.c:482
kasan_report+0x118/0x150 mm/kasan/report.c:595
vhci_send_cmd_submit drivers/usb/usbip/vhci_tx.c:69 [inline]
vhci_tx_loop+0x38e/0x1a80 drivers/usb/usbip/vhci_tx.c:241
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>

Allocated by task 6078:
kasan_save_stack mm/kasan/common.c:56 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
poison_kmalloc_redzone mm/kasan/common.c:397 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:414
kasan_kmalloc include/linux/kasan.h:262 [inline]
__kmalloc_cache_noprof+0x1fb/0x6d0 mm/slub.c:5776
kmalloc_noprof include/linux/slab.h:957 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
vhci_tx_urb drivers/usb/usbip/vhci_hcd.c:674 [inline]
vhci_urb_enqueue+0x5cd/0xe30 drivers/usb/usbip/vhci_hcd.c:829
usb_hcd_submit_urb+0x323/0x1b60 drivers/usb/core/hcd.c:1546
usb_start_wait_urb+0x115/0x4f0 drivers/usb/core/message.c:59
usb_internal_control_msg drivers/usb/core/message.c:103 [inline]
usb_control_msg+0x232/0x3e0 drivers/usb/core/message.c:154
get_bMaxPacketSize0 drivers/usb/core/hub.c:4851 [inline]
hub_port_init+0xb1d/0x28d0 drivers/usb/core/hub.c:5047
hub_port_connect drivers/usb/core/hub.c:5496 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
port_event drivers/usb/core/hub.c:5871 [inline]
hub_event+0x25b3/0x4f30 drivers/usb/core/hub.c:5953
process_one_work kernel/workqueue.c:3257 [inline]
process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Freed by task 11777:
kasan_save_stack mm/kasan/common.c:56 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:252 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
kasan_slab_free include/linux/kasan.h:234 [inline]
slab_free_hook mm/slub.c:2540 [inline]
slab_free mm/slub.c:6668 [inline]
kfree+0x1bd/0x900 mm/slub.c:6876
pickup_urb_and_free_priv+0x225/0x400 drivers/usb/usbip/vhci_rx.c:46
vhci_recv_ret_submit drivers/usb/usbip/vhci_rx.c:65 [inline]
vhci_rx_pdu drivers/usb/usbip/vhci_rx.c:242 [inline]
vhci_rx_loop+0x39f/0x9d0 drivers/usb/usbip/vhci_rx.c:265
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

The buggy address belongs to the object at ffff888033c85f80
which belongs to the cache kmalloc-64 of size 64
The buggy address is located 32 bytes inside of
freed 64-byte region [ffff888033c85f80, ffff888033c85fc0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x33c85
flags: 0x80000000000000(node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000000 ffff88813ff268c0 ffffea0000cc9bc0 dead000000000004
raw: 0000000000000000 0000000000200020 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 5153, tgid 5153 (start-stop-daem), ts 24440846967, free_ts 22870254625
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x234/0x290 mm/page_alloc.c:1846
prep_new_page mm/page_alloc.c:1854 [inline]
get_page_from_freelist+0x28c0/0x2960 mm/page_alloc.c:3915
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486
alloc_slab_page mm/slub.c:3075 [inline]
allocate_slab+0x86/0x3b0 mm/slub.c:3248
new_slab mm/slub.c:3302 [inline]
___slab_alloc+0xb10/0x1400 mm/slub.c:4656
__slab_alloc+0xc6/0x1f0 mm/slub.c:4779
__slab_alloc_node mm/slub.c:4855 [inline]
slab_alloc_node mm/slub.c:5251 [inline]
__do_kmalloc_node mm/slub.c:5656 [inline]
__kmalloc_noprof+0x15f/0x7e0 mm/slub.c:5669
kmalloc_noprof include/linux/slab.h:961 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
tomoyo_encode2 security/tomoyo/realpath.c:45 [inline]
tomoyo_encode+0x28b/0x550 security/tomoyo/realpath.c:80
tomoyo_realpath_from_path+0x58d/0x5d0 security/tomoyo/realpath.c:283
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x213/0x4b0 security/tomoyo/file.c:822
security_inode_getattr+0x12f/0x330 security/security.c:1869
vfs_getattr fs/stat.c:259 [inline]
vfs_fstat fs/stat.c:281 [inline]
__do_sys_newfstat fs/stat.c:555 [inline]
__se_sys_newfstat fs/stat.c:550 [inline]
__x64_sys_newfstat+0xfc/0x200 fs/stat.c:550
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 1 tgid 1 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1395 [inline]
__free_frozen_pages+0xfe1/0x1170 mm/page_alloc.c:2943
kasan_depopulate_vmalloc_pte+0x6d/0x90 mm/kasan/shadow.c:484
apply_to_pte_range mm/memory.c:3182 [inline]
apply_to_pmd_range mm/memory.c:3226 [inline]
apply_to_pud_range mm/memory.c:3262 [inline]
apply_to_p4d_range mm/memory.c:3298 [inline]
__apply_to_page_range+0xb66/0x13d0 mm/memory.c:3334
__kasan_release_vmalloc+0xa2/0xd0 mm/kasan/shadow.c:602
kasan_release_vmalloc include/linux/kasan.h:592 [inline]
kasan_release_vmalloc_node mm/vmalloc.c:2282 [inline]
purge_vmap_node+0x214/0x8d0 mm/vmalloc.c:2299
__purge_vmap_area_lazy+0x77a/0xb00 mm/vmalloc.c:2389
_vm_unmap_aliases+0x718/0x7b0 mm/vmalloc.c:2983
change_page_attr_set_clr+0x308/0xfb0 arch/x86/mm/pat/set_memory.c:2082
change_page_attr_set arch/x86/mm/pat/set_memory.c:2123 [inline]
set_memory_nx+0xd6/0x110 arch/x86/mm/pat/set_memory.c:2312
free_init_pages arch/x86/mm/init.c:934 [inline]
free_kernel_image_pages+0x85/0x100 arch/x86/mm/init.c:953
kernel_init+0x31/0x1d0 init/main.c:1587
ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Memory state around the buggy address:
ffff888033c85e80: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff888033c85f00: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
>ffff888033c85f80: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffff888033c86000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888033c86080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup