Message-ID: <6948a6e6.050a0220.1b4e0c.002e.GAE@google.com>
Date: Sun, 21 Dec 2025 18:03:18 -0800
From: syzbot <syzbot+549021d06a2b557303bd@...kaller.appspotmail.com>
To: gregkh@...uxfoundation.org, i@...ithal.me, linux-kernel@...r.kernel.org, 
	linux-usb@...r.kernel.org, shuah@...nel.org, syzkaller-bugs@...glegroups.com, 
	valentina.manea.m@...il.com
Subject: [syzbot] [usb?] KASAN: slab-use-after-free Read in vhci_tx_loop

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=549021d06a2b557303bd
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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+549021d06a2b557303bd@...kaller.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
==================================================================


---
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