Re: [syzbot] [fs?] KASAN: slab-use-after-free Read in sysfs_emit

[syzbot]

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@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
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
==================================================================


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#syz test: git://repo/address.git branch-or-commit-hash
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