syzbot


KASAN: slab-use-after-free Read in vhci_tx_loop

Status: upstream: reported on 2025/12/22 02:03
Subsystems: usb
[Documentation on labels]
Reported-by: syzbot+549021d06a2b557303bd@syzkaller.appspotmail.com
First crash: 125d, last: 22h58m
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
a22cff4a-a72a-4885-8b1e-285a4b367ef5 repro KASAN: slab-use-after-free Read in vhci_tx_loop 2026/03/06 21:56 2026/03/06 21:56 2026/03/06 22:06 31e9c887f7dc24e04b3ca70d0d54fc34141844b0
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [usb?] KASAN: slab-use-after-free Read in vhci_tx_loop 0 (1) 2025/12/22 02:03
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream general protection fault in vhci_tx_loop usb 2 1 479d 475d 0/29 auto-obsoleted due to no activity on 2025/03/28 12:39
linux-5.15 KASAN: use-after-free Read in vhci_tx_loop 19 1 386d 386d 0/3 auto-obsoleted due to no activity on 2025/07/09 17:53

Sample crash report:
==================================================================
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+0x3e9/0x1c50 drivers/usb/usbip/vhci_tx.c:241
Read of s[  605.420817][T12345] Read of size 8 at addr ffff8880402b9920 by task vhci_tx/12345

CPU: 1 UID: 0 PID: 12345 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 03/18/2026
Call Trace:
 <TASK>
 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
 vhci_send_cmd_submit drivers/usb/usbip/vhci_tx.c:69 [inline]
 vhci_tx_loop+0x3e9/0x1c50 drivers/usb/usbip/vhci_tx.c:241
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 10659:
 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]
 __kmalloc_cache_noprof+0x3a6/0x690 mm/slub.c:5415
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 vhci_tx_urb drivers/usb/usbip/vhci_hcd.c:674 [inline]
 vhci_urb_enqueue+0x5c9/0xe10 drivers/usb/usbip/vhci_hcd.c:829
 usb_hcd_submit_urb+0x323/0x1b50 drivers/usb/core/hcd.c:1542
 usb_start_wait_urb+0x13f/0x5b0 drivers/usb/core/message.c:62
 usb_internal_control_msg drivers/usb/core/message.c:117 [inline]
 usb_control_msg+0x234/0x3e0 drivers/usb/core/message.c:167
 get_bMaxPacketSize0 drivers/usb/core/hub.c:4851 [inline]
 hub_port_init+0xb1e/0x28c0 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+0x25d3/0x4f60 drivers/usb/core/hub.c:5953
 process_one_work kernel/workqueue.c:3302 [inline]
 process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385
 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 12338:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 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:2689 [inline]
 slab_free mm/slub.c:6246 [inline]
 kfree+0x1c5/0x6c0 mm/slub.c:6561
 pickup_urb_and_free_priv+0x225/0x3f0 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+0x3c5/0xa00 drivers/usb/usbip/vhci_rx.c:265
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff8880402b9900
 which belongs to the cache kmalloc-64 of size 64
The buggy address is located 32 bytes inside of
 freed 64-byte region [ffff8880402b9900, ffff8880402b9940)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x402b9
flags: 0x80000000000000(node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000000 ffff88801a01e8c0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800200020 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 0xd2c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5464, tgid 5464 (dhcpcd), ts 51114036279, free_ts 49690652007
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x231/0x280 mm/page_alloc.c:1860
 prep_new_page mm/page_alloc.c:1868 [inline]
 get_page_from_freelist+0x27c8/0x2840 mm/page_alloc.c:3948
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5228
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab+0x77/0x660 mm/slub.c:3467
 new_slab mm/slub.c:3525 [inline]
 refill_objects+0x33c/0x3d0 mm/slub.c:7251
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x373/0x720 mm/slub.c:4651
 alloc_from_pcs mm/slub.c:4749 [inline]
 slab_alloc_node mm/slub.c:4883 [inline]
 __do_kmalloc_node mm/slub.c:5294 [inline]
 __kmalloc_noprof+0x530/0x7b0 mm/slub.c:5307
 kmalloc_noprof include/linux/slab.h:954 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 tomoyo_commit_ok+0x29/0x1d0 security/tomoyo/memory.c:76
 tomoyo_update_domain+0x54a/0x880 security/tomoyo/domain.c:139
 tomoyo_update_path_acl security/tomoyo/file.c:402 [inline]
 tomoyo_write_file+0x3d1/0xc50 security/tomoyo/file.c:1027
 tomoyo_write_domain2 security/tomoyo/common.c:1160 [inline]
 tomoyo_add_entry security/tomoyo/common.c:2177 [inline]
 tomoyo_supervisor+0x1208/0x1570 security/tomoyo/common.c:2238
 tomoyo_audit_path_log security/tomoyo/file.c:169 [inline]
 tomoyo_path_permission+0x25a/0x380 security/tomoyo/file.c:592
 tomoyo_check_open_permission+0x2b2/0x470 security/tomoyo/file.c:782
 security_file_open+0xa9/0x240 security/security.c:2739
 do_dentry_open+0x4c0/0x13e0 fs/open.c:924
 vfs_open+0x3b/0x350 fs/open.c:1079
page last free pid 28 tgid 28 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1404 [inline]
 __free_frozen_pages+0xfa6/0x10f0 mm/page_alloc.c:2945
 rcu_do_batch kernel/rcu/tree.c:2617 [inline]
 rcu_core kernel/rcu/tree.c:2869 [inline]
 rcu_cpu_kthread+0x99e/0x1470 kernel/rcu/tree.c:2957
 smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff8880402b9800: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff8880402b9880: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
>ffff8880402b9900: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                               ^
 ffff8880402b9980: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff8880402b9a00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/17 17:38 upstream 43cfbdda5af6 24ecfc1e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in vhci_tx_loop
2025/12/31 01:00 upstream dbf8fe85a16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in vhci_tx_loop
2025/12/17 19:07 upstream ea1013c15392 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in vhci_tx_loop
2026/04/21 06:59 linux-next 97e797263a5e 3f2e655b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in vhci_tx_loop
2026/01/15 07:10 linux-next 9b7977f9e39b d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce general protection fault in vhci_tx_loop
* Struck through repros no longer work on HEAD.