From: syzbot <syzbot+302b9b575a06733ff60c@syzkaller.appspotmail.com>
To: dakr@kernel.org, driver-core@lists.linux.dev,
gregkh@linuxfoundation.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, rafael@kernel.org,
syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [fs?] KASAN: slab-use-after-free Read in sysfs_emit
Date: Mon, 31 Aug 2026 12:42:30 -0700 [thread overview]
Message-ID: <6a95d926.99925153.16bd3d.0005.GAE@google.com> (raw)
In-Reply-To: <6a74a76d.ec7c9571.3ac9bb.0056.GAE@google.com>
syzbot has found a reproducer for the following issue on:
HEAD commit: f1b8fa82cab7 Merge branch 'for-next/core' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=13ca3379580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d1128bc53f2ef7f3
dashboard link: https://syzkaller.appspot.com/bug?extid=302b9b575a06733ff60c
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13caad9e580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=136de379580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/932d85a2bda2/disk-f1b8fa82.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5b6b8fb76e8d/vmlinux-f1b8fa82.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c246b61ee396/Image-f1b8fa82.gz.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+302b9b575a06733ff60c@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: slab-use-after-free in string_nocheck+0xd8/0x140 lib/vsprintf.c:648
Read of size 1 at addr ffff0000d4016758 by task udevd/4787
CPU: 0 UID: 0 PID: 4787 Comm: udevd Not tainted syzkaller #0 PREEMPT
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
Call trace:
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
__dump_stack+0x30/0x40 lib/dump_stack.c:94
dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
print_address_description+0xb0/0x238 mm/kasan/report.c:378
print_report+0x68/0x84 mm/kasan/report.c:482
kasan_report+0x8c/0xc4 mm/kasan/report.c:595
__asan_report_load1_noabort+0x20/0x2c mm/kasan/report_generic.c:378
string_nocheck+0xd8/0x140 lib/vsprintf.c:648
string+0x8c/0xc8 lib/vsprintf.c:730
vsnprintf+0x880/0xd10 lib/vsprintf.c:2945
vscnprintf+0x6c/0xd4 lib/vsprintf.c:3014
sysfs_emit+0x110/0x184 fs/sysfs/file.c:761
input_dev_show_name+0x60/0x74 drivers/input/input.c:1282
dev_attr_show+0x60/0xd0 drivers/base/core.c:2487
sysfs_kf_seq_show+0x1e0/0x2fc fs/sysfs/file.c:65
kernfs_seq_show+0xf0/0x130 fs/kernfs/file.c:216
seq_read_iter+0x39c/0xbe8 fs/seq_file.c:231
kernfs_fop_read_iter+0x13c/0x414 fs/kernfs/file.c:290
new_sync_read fs/read_write.c:493 [inline]
vfs_read+0x498/0x8c8 fs/read_write.c:574
ksys_read+0x12c/0x228 fs/read_write.c:716
__do_sys_read fs/read_write.c:725 [inline]
__se_sys_read fs/read_write.c:723 [inline]
__arm64_sys_read+0x84/0x98 fs/read_write.c:723
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:758
el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590
Allocated by task 4754:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x40/0x78 mm/kasan/common.c:78
kasan_save_alloc_info+0x40/0x50 mm/kasan/generic.c:570
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x9c/0xb4 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__kmalloc_cache_noprof+0x2e8/0x5ec mm/slub.c:5489
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
redrat3_dev_probe+0x3a4/0x1e90 drivers/media/rc/redrat3.c:1023
usb_probe_interface+0x308/0x788 drivers/usb/core/driver.c:396
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x29c/0x800 drivers/base/dd.c:706
__driver_probe_device+0x1e0/0x350 drivers/base/dd.c:868
driver_probe_device+0x6c/0x19c drivers/base/dd.c:898
__device_attach_driver+0x198/0x2f8 drivers/base/dd.c:1026
bus_for_each_drv+0x144/0x1dc drivers/base/bus.c:500
__device_attach+0x248/0x390 drivers/base/dd.c:1098
device_initial_probe+0x90/0xc8 drivers/base/dd.c:1153
bus_probe_device+0x58/0x120 drivers/base/bus.c:620
device_add+0x6cc/0x9e0 drivers/base/core.c:3772
usb_set_configuration+0x1184/0x158c drivers/usb/core/message.c:2268
usb_generic_driver_probe+0x8c/0x148 drivers/usb/core/generic.c:250
usb_probe_device+0x114/0x2b0 drivers/usb/core/driver.c:291
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x29c/0x800 drivers/base/dd.c:706
__driver_probe_device+0x1e0/0x350 drivers/base/dd.c:868
driver_probe_device+0x6c/0x19c drivers/base/dd.c:898
__device_attach_driver+0x198/0x2f8 drivers/base/dd.c:1026
bus_for_each_drv+0x144/0x1dc drivers/base/bus.c:500
__device_attach+0x248/0x390 drivers/base/dd.c:1098
device_initial_probe+0x90/0xc8 drivers/base/dd.c:1153
bus_probe_device+0x58/0x120 drivers/base/bus.c:620
device_add+0x6cc/0x9e0 drivers/base/core.c:3772
usb_new_device+0x9c4/0x11f8 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+0x1ef0/0x39fc drivers/usb/core/hub.c:5961
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0x788/0x10b8 kernel/workqueue.c:3405
worker_thread+0x798/0xbd0 kernel/workqueue.c:3486
kthread+0x304/0x3d4 kernel/kthread.c:436
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:838
Freed by task 4754:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x40/0x78 mm/kasan/common.c:78
kasan_save_free_info+0x54/0x6c mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x74/0xa4 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+0x188/0x690 mm/slub.c:6692
redrat3_delete drivers/media/rc/redrat3.c:466 [inline]
redrat3_dev_probe+0x1008/0x1e90 drivers/media/rc/redrat3.c:1124
usb_probe_interface+0x308/0x788 drivers/usb/core/driver.c:396
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x29c/0x800 drivers/base/dd.c:706
__driver_probe_device+0x1e0/0x350 drivers/base/dd.c:868
driver_probe_device+0x6c/0x19c drivers/base/dd.c:898
__device_attach_driver+0x198/0x2f8 drivers/base/dd.c:1026
bus_for_each_drv+0x144/0x1dc drivers/base/bus.c:500
__device_attach+0x248/0x390 drivers/base/dd.c:1098
device_initial_probe+0x90/0xc8 drivers/base/dd.c:1153
bus_probe_device+0x58/0x120 drivers/base/bus.c:620
device_add+0x6cc/0x9e0 drivers/base/core.c:3772
usb_set_configuration+0x1184/0x158c drivers/usb/core/message.c:2268
usb_generic_driver_probe+0x8c/0x148 drivers/usb/core/generic.c:250
usb_probe_device+0x114/0x2b0 drivers/usb/core/driver.c:291
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x29c/0x800 drivers/base/dd.c:706
__driver_probe_device+0x1e0/0x350 drivers/base/dd.c:868
driver_probe_device+0x6c/0x19c drivers/base/dd.c:898
__device_attach_driver+0x198/0x2f8 drivers/base/dd.c:1026
bus_for_each_drv+0x144/0x1dc drivers/base/bus.c:500
__device_attach+0x248/0x390 drivers/base/dd.c:1098
device_initial_probe+0x90/0xc8 drivers/base/dd.c:1153
bus_probe_device+0x58/0x120 drivers/base/bus.c:620
device_add+0x6cc/0x9e0 drivers/base/core.c:3772
usb_new_device+0x9c4/0x11f8 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+0x1ef0/0x39fc drivers/usb/core/hub.c:5961
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0x788/0x10b8 kernel/workqueue.c:3405
worker_thread+0x798/0xbd0 kernel/workqueue.c:3486
kthread+0x304/0x3d4 kernel/kthread.c:436
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:838
The buggy address belongs to the object at ffff0000d4016000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1880 bytes inside of
freed 2048-byte region [ffff0000d4016000, ffff0000d4016800)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff0000d4011000 pfn:0x114010
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x5ffc00000000240(workingset|head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 05ffc00000000240 ffff0000c0002000 fffffdffc3830c10 fffffdffc3bffc10
raw: ffff0000d4011000 0000000800080005 00000000f5000000 0000000000000000
head: 05ffc00000000240 ffff0000c0002000 fffffdffc3830c10 fffffdffc3bffc10
head: ffff0000d4011000 0000000800080005 00000000f5000000 0000000000000000
head: 05ffc00000000003 fffffdffc3500401 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff0000d4016600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff0000d4016680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff0000d4016700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff0000d4016780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff0000d4016800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
---
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:[~2026-08-31 19:42 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-06 15:25 [syzbot] [fs?] KASAN: slab-use-after-free Read in sysfs_emit syzbot
2026-08-31 19:42 ` syzbot [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6a95d926.99925153.16bd3d.0005.GAE@google.com \
--to=syzbot+302b9b575a06733ff60c@syzkaller.appspotmail.com \
--cc=dakr@kernel.org \
--cc=driver-core@lists.linux.dev \
--cc=gregkh@linuxfoundation.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=rafael@kernel.org \
--cc=syzkaller-bugs@googlegroups.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox