[v6.1] KASAN: use-after-free Read in raw_ioctl

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fb28aa725e05 Linux 6.1.180
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12ca2649580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=bafe7af8336a320896e5
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17595e32580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9a6fe2a54d0f/disk-fb28aa72.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/742b23a1d931/vmlinux-fb28aa72.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b3f257c16d2e/bzImage-fb28aa72.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bafe7a...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in string_nocheck lib/vsprintf.c:643 [inline]
BUG: KASAN: use-after-free in string+0x204/0x290 lib/vsprintf.c:725
Read of size 1 at addr ffff88802837c5e0 by task syz.0.17/4481

CPU: 1 PID: 4481 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
print_address_description mm/kasan/report.c:316 [inline]
print_report+0xa8/0x210 mm/kasan/report.c:420
kasan_report+0x10b/0x140 mm/kasan/report.c:524
string_nocheck lib/vsprintf.c:643 [inline]
string+0x204/0x290 lib/vsprintf.c:725
vsnprintf+0x10db/0x1c20 lib/vsprintf.c:2805
snprintf+0xe5/0x140 lib/vsprintf.c:2940
set_dev_info drivers/base/core.c:4936 [inline]
dev_vprintk_emit+0x303/0x3de drivers/base/core.c:4946
dev_printk_emit+0xeb/0x139 drivers/base/core.c:4959
_dev_err+0x11b/0x16c drivers/base/core.c:5014
raw_ioctl_ep0_stall drivers/usb/gadget/legacy/raw_gadget.c:781 [inline]
raw_ioctl+0x2a2a/0x3cd0 drivers/usb/gadget/legacy/raw_gadget.c:1295
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f3a7a19dcab
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007f3a7af83f50 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f3a7a19dcab
RDX: 0000000000000000 RSI: 000000000000550c RDI: 0000000000000003
RBP: 00007f3a7a23500c R08: 0000000000000003 R09: 0000000000000409
R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
R13: 0000200000000080 R14: 00007f3a7a425fa0 R15: 00007ffe839b9608
</TASK>

Allocated by task 1:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
____kasan_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:384
kasan_kmalloc include/linux/kasan.h:211 [inline]
__do_kmalloc_node mm/slab_common.c:936 [inline]
__kmalloc_node_track_caller+0xb0/0x240 mm/slab_common.c:956
kvasprintf+0xe8/0x1a0 lib/kasprintf.c:25
kobject_set_name_vargs+0x5d/0x110 lib/kobject.c:265
dev_set_name+0xdf/0x130 drivers/base/core.c:3485
usb_add_gadget+0x474/0x6f0 drivers/usb/gadget/udc/core.c:1448
usb_add_gadget_udc_release+0x198/0x1e0 drivers/usb/gadget/udc/core.c:1506
dummy_udc_probe+0x686/0x780 drivers/usb/gadget/udc/dummy_hcd.c:1102
platform_probe+0x137/0x1c0 drivers/base/platform.c:1400
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x24a/0xb40 drivers/base/dd.c:638
__driver_probe_device+0x1f5/0x390 drivers/base/dd.c:804
driver_probe_device+0x4f/0x420 drivers/base/dd.c:834
__device_attach_driver+0x2c6/0x510 drivers/base/dd.c:962
bus_for_each_drv+0x184/0x210 drivers/base/bus.c:429
__device_attach+0x2a7/0x480 drivers/base/dd.c:1034
bus_probe_device+0xba/0x1d0 drivers/base/bus.c:489
device_add+0xbcf/0x1050 drivers/base/core.c:3712
platform_device_add+0x4bf/0x830 drivers/base/platform.c:717
dummy_hcd_init+0xc26/0x1167 drivers/usb/gadget/udc/dummy_hcd.c:2883
do_one_initcall+0x257/0x800 init/main.c:1309
do_initcall_level+0x13d/0x1ed init/main.c:1382
do_initcalls+0x4b/0x8a init/main.c:1398
kernel_init_freeable+0x401/0x5ab init/main.c:1637
kernel_init+0x19/0x1b0 init/main.c:1525
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Freed by task 4479:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1729 [inline]
slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755
slab_free mm/slub.c:3687 [inline]
__kmem_cache_free+0xb6/0x200 mm/slub.c:3700
kobject_cleanup lib/kobject.c:687 [inline]
kobject_release lib/kobject.c:712 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x25c/0x450 lib/kobject.c:729
dummy_udc_remove+0x54/0x60 drivers/usb/gadget/udc/dummy_hcd.c:1123
platform_remove+0x92/0xe0 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+0x47d/0x7c0 drivers/base/dd.c:1305
unbind_store+0x2e2/0x300 drivers/base/bus.c:193
kernfs_fop_write_iter+0x3a0/0x520 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+0x482/0x9a0 fs/read_write.c:584
ksys_write+0x14d/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88802837c5e0
which belongs to the cache kmalloc-16 of size 16
The buggy address is located 0 bytes inside of
16-byte region [ffff88802837c5e0, ffff88802837c5f0)

The buggy address belongs to the physical page:
page:ffffea0000a0df00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2837c
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 dead000000000100 dead000000000122 ffff8880174413c0
raw: 0000000000000000 0000000000800080 00000001ffffffff 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 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, tgid 1 (swapper/0), ts 15380822738, free_ts 0
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2560
prep_new_page mm/page_alloc.c:2567 [inline]
get_page_from_freelist+0x206b/0x2180 mm/page_alloc.c:4358
__alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5658
alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2115
alloc_slab_page+0x5d/0x180 mm/slub.c:1799
allocate_slab mm/slub.c:1944 [inline]
new_slab+0x87/0x2d0 mm/slub.c:1997
___slab_alloc+0xbc5/0x1240 mm/slub.c:3154
__slab_alloc mm/slub.c:3240 [inline]
slab_alloc_node mm/slub.c:3325 [inline]
__kmem_cache_alloc_node+0x126/0x270 mm/slub.c:3398
__do_kmalloc_node mm/slab_common.c:935 [inline]
__kmalloc+0xa3/0x240 mm/slab_common.c:949
kmalloc include/linux/slab.h:568 [inline]
kzalloc include/linux/slab.h:699 [inline]
rh_call_control drivers/usb/core/hcd.c:512 [inline]
rh_urb_enqueue drivers/usb/core/hcd.c:846 [inline]
usb_hcd_submit_urb+0x793/0x1970 drivers/usb/core/hcd.c:1554
usb_start_wait_urb+0x13c/0x580 drivers/usb/core/message.c:61
usb_internal_control_msg drivers/usb/core/message.c:116 [inline]
usb_control_msg+0x231/0x3e0 drivers/usb/core/message.c:166
get_hub_descriptor drivers/usb/core/hub.c:426 [inline]
hub_configure drivers/usb/core/hub.c:1461 [inline]
hub_probe+0xfcf/0x3790 drivers/usb/core/hub.c:1975
usb_probe_interface+0x5be/0xae0 drivers/usb/core/driver.c:396
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x24a/0xb40 drivers/base/dd.c:638
__driver_probe_device+0x1f5/0x390 drivers/base/dd.c:804
page_owner free stack trace missing

Memory state around the buggy address:
ffff88802837c480: 00 04 fc fc 00 01 fc fc 00 01 fc fc 00 01 fc fc
ffff88802837c500: 00 04 fc fc 00 04 fc fc 00 04 fc fc fa fb fc fc
>ffff88802837c580: fa fb fc fc 00 04 fc fc 00 04 fc fc fa fb fc fc
^
ffff88802837c600: 00 01 fc fc 00 01 fc fc 00 04 fc fc 00 04 fc fc
ffff88802837c680: 00 04 fc fc 00 04 fc fc 00 04 fc fc 00 04 fc fc
==================================================================


---
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