[syzbot] [usb?] KASAN: slab-use-after-free Read in stub_rx_loop

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 48a5a7ab8d6a Merge tag 'v7.2-rc4-smb3-client-fixes' of git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=113c32ea580000
kernel config: https://syzkaller.appspot.com/x/.config?x=20c9876b0f77b546
dashboard link: https://syzkaller.appspot.com/bug?extid=06fa667a0931a3430026
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-48a5a7ab.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cca5551ec121/vmlinux-48a5a7ab.xz
kernel image: https://storage.googleapis.com/syzbot-assets/30b6e710a3ae/bzImage-48a5a7ab.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+06fa66...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:609 [inline]
BUG: KASAN: slab-use-after-free in stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
BUG: KASAN: slab-use-after-free in stub_rx_loop+0x2965/0x2ee0 drivers/usb/usbip/stub_rx.c:707
Read of size 4 at addr ffff888012cacdb0 by task stub_rx/5324

CPU: 0 UID: 0 PID: 5324 Comm: stub_rx Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
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
stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:609 [inline]
stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
stub_rx_loop+0x2965/0x2ee0 drivers/usb/usbip/stub_rx.c:707
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 5324:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
unpoison_slab_object mm/kasan/common.c:340 [inline]
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4612 [inline]
slab_alloc_node mm/slub.c:4945 [inline]
kmem_cache_alloc_noprof+0x2a0/0x5f0 mm/slub.c:4959
stub_priv_alloc drivers/usb/usbip/stub_rx.c:314 [inline]
stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:490 [inline]
stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
stub_rx_loop+0xad9/0x2ee0 drivers/usb/usbip/stub_rx.c:707
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 5325:
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:2705 [inline]
slab_free mm/slub.c:6405 [inline]
kmem_cache_free+0x182/0x650 mm/slub.c:6532
stub_send_ret_submit drivers/usb/usbip/stub_tx.c:333 [inline]
stub_tx_loop+0x1b16/0x2800 drivers/usb/usbip/stub_tx.c:437
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 ffff888012cacd80
which belongs to the cache stub_priv of size 64
The buggy address is located 48 bytes inside of
freed 64-byte region [ffff888012cacd80, ffff888012cacdc0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888012cace00 pfn:0x12cac
flags: 0xfff00000000200(workingset|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000200 ffff888033fd4280 ffff8880340e27c8 ffff8880340e27c8
raw: ffff888012cace00 000000080020001c 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5324, tgid 5324 (stub_rx), ts 94362120884, free_ts 93984048542
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
prep_new_page mm/page_alloc.c:1867 [inline]
get_page_from_freelist+0x21fa/0x2270 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
alloc_slab_page mm/slub.c:3294 [inline]
allocate_slab+0x79/0x5e0 mm/slub.c:3408
new_slab mm/slub.c:3454 [inline]
refill_objects+0x2d5/0x350 mm/slub.c:7338
refill_sheaf mm/slub.c:2832 [inline]
__pcs_replace_empty_main+0x2bf/0x6b0 mm/slub.c:4703
alloc_from_pcs mm/slub.c:4801 [inline]
slab_alloc_node mm/slub.c:4933 [inline]
kmem_cache_alloc_noprof+0x382/0x5f0 mm/slub.c:4959
stub_priv_alloc drivers/usb/usbip/stub_rx.c:314 [inline]
stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:490 [inline]
stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
stub_rx_loop+0xad9/0x2ee0 drivers/usb/usbip/stub_rx.c:707
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
page last free pid 4993 tgid 4993 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1406 [inline]
__free_frozen_pages+0xc1e/0xd10 mm/page_alloc.c:2950
__slab_free+0x274/0x2c0 mm/slub.c:5767
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:4612 [inline]
slab_alloc_node mm/slub.c:4945 [inline]
kmem_cache_alloc_node_noprof+0x355/0x610 mm/slub.c:5017
__alloc_skb+0x1d7/0x7a0 net/core/skbuff.c:704
alloc_skb include/linux/skbuff.h:1384 [inline]
alloc_skb_with_frags+0xc6/0x760 net/core/skbuff.c:6769
sock_alloc_send_pskb+0x878/0x990 net/core/sock.c:3013
unix_dgram_sendmsg+0x4fe/0x1870 net/unix/af_unix.c:2136
sock_sendmsg_nosec+0x13a/0x180 net/socket.c:775
__sock_sendmsg net/socket.c:790 [inline]
sock_write_iter+0x2de/0x3e0 net/socket.c:1241
do_iter_readv_writev+0x612/0x8c0 fs/read_write.c:-1
vfs_writev+0x343/0x990 fs/read_write.c:1058
do_writev+0x154/0x2e0 fs/read_write.c:1104
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94

Memory state around the buggy address:
ffff888012cacc80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888012cacd00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888012cacd80: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffff888012cace00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888012cace80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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