From: syzbot <syzbot+2a123f6269da57ffefaa@syzkaller.appspotmail.com>
To: dmitry.torokhov@gmail.com, linux-input@vger.kernel.org,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [input?] KASAN: slab-use-after-free Read in input_dev_uevent (2)
Date: Sun, 09 Aug 2026 03:44:35 -0700 [thread overview]
Message-ID: <6a785a13.9c11d2ce.289b96.00cd.GAE@google.com> (raw)
In-Reply-To: <6a784ada.01d0871a.3a0d52.0082.GAE@google.com>
syzbot has found a reproducer for the following issue on:
HEAD commit: 06cf61899d64 Merge tag 'x86-urgent-2026-08-08' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10641132580000
kernel config: https://syzkaller.appspot.com/x/.config?x=aaf0da806f995318
dashboard link: https://syzkaller.appspot.com/bug?extid=2a123f6269da57ffefaa
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=15a45fb9580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16837fb9580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/26f384ba081d/disk-06cf6189.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/019cb7a0fac6/vmlinux-06cf6189.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fc9d4a72e1ed/bzImage-06cf6189.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2a123f6269da57ffefaa@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: slab-use-after-free in string_nocheck lib/vsprintf.c:648 [inline]
BUG: KASAN: slab-use-after-free in string+0x216/0x2d0 lib/vsprintf.c:730
Read of size 1 at addr ffff88802b56ac0a by task udevd/4979
CPU: 0 UID: 0 PID: 4979 Comm: udevd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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
string_nocheck lib/vsprintf.c:648 [inline]
string+0x216/0x2d0 lib/vsprintf.c:730
vsnprintf+0x74a/0xef0 lib/vsprintf.c:2945
add_uevent_var+0x1ce/0x460 lib/kobject_uevent.c:682
input_dev_uevent+0x170/0x6e0 drivers/input/input.c:1676
dev_uevent+0x537/0x870 drivers/base/core.c:2779
uevent_show+0x1a0/0x310 drivers/base/core.c:2826
dev_attr_show+0x58/0xc0 drivers/base/core.c:2487
sysfs_kf_seq_show+0x331/0x490 fs/sysfs/file.c:65
seq_read_iter+0x463/0xca0 fs/seq_file.c:231
new_sync_read fs/read_write.c:493 [inline]
vfs_read+0x595/0xa80 fs/read_write.c:574
ksys_read+0x150/0x270 fs/read_write.c:716
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb92b4a7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffd5470cba0 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007fb92bc14880 RCX: 00007fb92b4a7407
RDX: 0000000000001000 RSI: 000055aa6b59e2c0 RDI: 000000000000000c
RBP: 00007fb92b5efff0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000000a
R13: 00007fb92b5efea0 R14: 0000000000000000 R15: 000055aa6b55a7a0
</TASK>
Allocated by task 10:
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+0x32d/0x660 mm/slub.c:5489
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
sur40_probe+0x16d/0xfa0 drivers/input/touchscreen/sur40.c:675
usb_probe_interface+0x653/0xc60 drivers/usb/core/driver.c:396
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x254/0xae0 drivers/base/dd.c:706
__driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
__device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
__device_attach+0x2c4/0x450 drivers/base/dd.c:1098
device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
bus_probe_device+0x12a/0x220 drivers/base/bus.c:620
device_add+0x7d7/0xb80 drivers/base/core.c:3772
usb_set_configuration+0x1ad8/0x2180 drivers/usb/core/message.c:2268
usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
usb_probe_device+0x1c3/0x3b0 drivers/usb/core/driver.c:291
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x254/0xae0 drivers/base/dd.c:706
__driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
__device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
__device_attach+0x2c4/0x450 drivers/base/dd.c:1098
device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
bus_probe_device+0x12a/0x220 drivers/base/bus.c:620
device_add+0x7d7/0xb80 drivers/base/core.c:3772
usb_new_device+0x9aa/0x1690 drivers/usb/core/hub.c:2703
hub_port_connect drivers/usb/core/hub.c:5575 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5715 [inline]
port_event drivers/usb/core/hub.c:5879 [inline]
hub_event+0x28e8/0x4d30 drivers/usb/core/hub.c:5961
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
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 10:
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:2677 [inline]
slab_free mm/slub.c:6377 [inline]
kfree+0x1c5/0x640 mm/slub.c:6692
sur40_probe+0x918/0xfa0 drivers/input/touchscreen/sur40.c:816
usb_probe_interface+0x653/0xc60 drivers/usb/core/driver.c:396
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x254/0xae0 drivers/base/dd.c:706
__driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
__device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
__device_attach+0x2c4/0x450 drivers/base/dd.c:1098
device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
bus_probe_device+0x12a/0x220 drivers/base/bus.c:620
device_add+0x7d7/0xb80 drivers/base/core.c:3772
usb_set_configuration+0x1ad8/0x2180 drivers/usb/core/message.c:2268
usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
usb_probe_device+0x1c3/0x3b0 drivers/usb/core/driver.c:291
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x254/0xae0 drivers/base/dd.c:706
__driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
__device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
__device_attach+0x2c4/0x450 drivers/base/dd.c:1098
device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
bus_probe_device+0x12a/0x220 drivers/base/bus.c:620
device_add+0x7d7/0xb80 drivers/base/core.c:3772
usb_new_device+0x9aa/0x1690 drivers/usb/core/hub.c:2703
hub_port_connect drivers/usb/core/hub.c:5575 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5715 [inline]
port_event drivers/usb/core/hub.c:5879 [inline]
hub_event+0x28e8/0x4d30 drivers/usb/core/hub.c:5961
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
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 ffff88802b56a000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 3082 bytes inside of
freed 4096-byte region [ffff88802b56a000, ffff88802b56b000)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2b568
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b005140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b005140 dead000000000100 dead000000000122
head: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4989, tgid 4989 (udevd), ts 44031026238, free_ts 43938304635
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:3266 [inline]
allocate_slab+0x79/0x5e0 mm/slub.c:3380
new_slab mm/slub.c:3426 [inline]
refill_objects+0x2d5/0x350 mm/slub.c:7310
refill_sheaf mm/slub.c:2804 [inline]
__pcs_replace_empty_main+0x2bf/0x6b0 mm/slub.c:4675
alloc_from_pcs mm/slub.c:4773 [inline]
slab_alloc_node mm/slub.c:4905 [inline]
__do_kmalloc_node mm/slub.c:5333 [inline]
__kmalloc_noprof+0x485/0x720 mm/slub.c:5359
_kmalloc_noprof include/linux/slab.h:992 [inline]
tomoyo_realpath_from_path+0xef/0x640 security/tomoyo/realpath.c:251
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x283/0x560 security/tomoyo/file.c:827
security_inode_getattr+0x12b/0x310 security/security.c:1895
vfs_getattr+0x23/0x70 fs/stat.c:259
vfs_statx_path+0x2b/0x230 fs/stat.c:299
vfs_statx+0x12e/0x200 fs/stat.c:356
vfs_fstatat+0x11b/0x170 fs/stat.c:373
__do_sys_newfstatat fs/stat.c:538 [inline]
__se_sys_newfstatat fs/stat.c:532 [inline]
__x64_sys_newfstatat+0x151/0x200 fs/stat.c:532
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
page last free pid 4986 tgid 4986 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:5741
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:4584 [inline]
slab_alloc_node mm/slub.c:4917 [inline]
kmem_cache_alloc_noprof+0x2a0/0x5f0 mm/slub.c:4931
alloc_filename fs/namei.c:147 [inline]
do_getname+0x2e/0x250 fs/namei.c:187
class_filename_uflags_constructor include/linux/fs.h:2567 [inline]
do_fchmodat+0xca/0x230 fs/open.c:678
__do_sys_chmod fs/open.c:706 [inline]
__se_sys_chmod fs/open.c:704 [inline]
__x64_sys_chmod+0x62/0x70 fs/open.c:704
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Memory state around the buggy address:
ffff88802b56ab00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802b56ab80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802b56ac00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802b56ac80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802b56ad00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
prev parent reply other threads:[~2026-08-09 10:44 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-09 9:39 [syzbot] [input?] KASAN: slab-use-after-free Read in input_dev_uevent (2) syzbot
2026-08-09 10:44 ` syzbot [this message]
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