From: syzbot <syzbot+a56aa983ce6a1bf12485@syzkaller.appspotmail.com>
To: dakr@kernel.org, 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 driver_remove_file
Date: Sat, 20 Sep 2025 21:04:28 -0700 [thread overview]
Message-ID: <68cf794c.050a0220.13cd81.002a.GAE@google.com> (raw)
In-Reply-To: <6888afe6.050a0220.f0410.0005.GAE@google.com>
syzbot has found a reproducer for the following issue on:
HEAD commit: 3b08f56fbbb9 Merge tag 'x86-urgent-2025-09-20' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14ce5858580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8f01d8629880e620
dashboard link: https://syzkaller.appspot.com/bug?extid=a56aa983ce6a1bf12485
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15571534580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=152f7e42580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/50f34afb9e37/disk-3b08f56f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/421a8470ac48/vmlinux-3b08f56f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/218f92cd0c4d/bzImage-3b08f56f.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a56aa983ce6a1bf12485@syzkaller.appspotmail.com
comedi comedi1: c6xdigio: I/O port conflict (0x401,3)
==================================================================
BUG: KASAN: slab-use-after-free in sysfs_remove_file_ns+0x63/0x70 fs/sysfs/file.c:522
Read of size 8 at addr ffff88807d7e6e30 by task syz.0.18/6035
CPU: 1 UID: 0 PID: 6035 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xcd/0x630 mm/kasan/report.c:482
kasan_report+0xe0/0x110 mm/kasan/report.c:595
sysfs_remove_file_ns+0x63/0x70 fs/sysfs/file.c:522
sysfs_remove_file include/linux/sysfs.h:777 [inline]
driver_remove_file drivers/base/driver.c:201 [inline]
driver_remove_file+0x4a/0x60 drivers/base/driver.c:197
remove_bind_files drivers/base/bus.c:605 [inline]
bus_remove_driver+0x224/0x2c0 drivers/base/bus.c:743
driver_unregister+0x76/0xb0 drivers/base/driver.c:277
comedi_device_detach_locked+0x12f/0xa50 drivers/comedi/drivers.c:207
comedi_device_detach+0x67/0xb0 drivers/comedi/drivers.c:215
comedi_device_attach+0x43d/0x900 drivers/comedi/drivers.c:1011
do_devconfig_ioctl+0x1b1/0x710 drivers/comedi/comedi_fops.c:872
comedi_unlocked_ioctl+0x165d/0x2f00 drivers/comedi/comedi_fops.c:2178
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:598 [inline]
__se_sys_ioctl fs/ioctl.c:584 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:584
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f623a78ec29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe5ded2158 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f623a9d5fa0 RCX: 00007f623a78ec29
RDX: 0000200000000080 RSI: 0000000040946400 RDI: 0000000000000004
RBP: 00007f623a811e41 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f623a9d5fa0 R14: 00007f623a9d5fa0 R15: 0000000000000003
</TASK>
Allocated by task 6034:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:405
kmalloc_noprof include/linux/slab.h:905 [inline]
kzalloc_noprof include/linux/slab.h:1039 [inline]
bus_add_driver+0x92/0x690 drivers/base/bus.c:662
driver_register+0x15c/0x4b0 drivers/base/driver.c:249
c6xdigio_attach drivers/comedi/drivers/c6xdigio.c:253 [inline]
c6xdigio_attach+0xa3/0x4b0 drivers/comedi/drivers/c6xdigio.c:238
comedi_device_attach+0x3b0/0x900 drivers/comedi/drivers.c:1007
do_devconfig_ioctl+0x1b1/0x710 drivers/comedi/comedi_fops.c:872
comedi_unlocked_ioctl+0x165d/0x2f00 drivers/comedi/comedi_fops.c:2178
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:598 [inline]
__se_sys_ioctl fs/ioctl.c:584 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:584
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 6034:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:243 [inline]
__kasan_slab_free+0x60/0x70 mm/kasan/common.c:275
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2422 [inline]
slab_free mm/slub.c:4695 [inline]
kfree+0x2b4/0x4d0 mm/slub.c:4894
kobject_cleanup lib/kobject.c:689 [inline]
kobject_release lib/kobject.c:720 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x1e7/0x5a0 lib/kobject.c:737
bus_remove_driver+0x16e/0x2c0 drivers/base/bus.c:749
driver_unregister+0x76/0xb0 drivers/base/driver.c:277
comedi_device_detach_locked+0x12f/0xa50 drivers/comedi/drivers.c:207
comedi_device_detach+0x67/0xb0 drivers/comedi/drivers.c:215
comedi_device_attach+0x43d/0x900 drivers/comedi/drivers.c:1011
do_devconfig_ioctl+0x1b1/0x710 drivers/comedi/comedi_fops.c:872
comedi_unlocked_ioctl+0x165d/0x2f00 drivers/comedi/comedi_fops.c:2178
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:598 [inline]
__se_sys_ioctl fs/ioctl.c:584 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:584
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff88807d7e6e00
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 48 bytes inside of
freed 256-byte region [ffff88807d7e6e00, ffff88807d7e6f00)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7d7e6
head: order:1 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 ffff88801b841b40 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b841b40 dead000000000122 0000000000000000
head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffea0001f5f981 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5959, tgid 5959 (syz-executor), ts 73428545830, free_ts 73053846504
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1851
prep_new_page mm/page_alloc.c:1859 [inline]
get_page_from_freelist+0x132b/0x38e0 mm/page_alloc.c:3858
__alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:5148
alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416
alloc_slab_page mm/slub.c:2492 [inline]
allocate_slab mm/slub.c:2660 [inline]
new_slab+0x247/0x330 mm/slub.c:2714
___slab_alloc+0xcf2/0x1750 mm/slub.c:3901
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3992
__slab_alloc_node mm/slub.c:4067 [inline]
slab_alloc_node mm/slub.c:4228 [inline]
__do_kmalloc_node mm/slub.c:4375 [inline]
__kmalloc_noprof+0x2f2/0x510 mm/slub.c:4388
kmalloc_noprof include/linux/slab.h:909 [inline]
kmalloc_array_noprof include/linux/slab.h:948 [inline]
__list_lru_init+0xe8/0x4c0 mm/list_lru.c:588
alloc_super+0x904/0xbd0 fs/super.c:391
sget_fc+0x116/0xc20 fs/super.c:761
vfs_get_super fs/super.c:1320 [inline]
get_tree_nodev+0x28/0x190 fs/super.c:1344
vfs_get_tree+0x8e/0x340 fs/super.c:1815
do_new_mount fs/namespace.c:3808 [inline]
path_mount+0x1513/0x2000 fs/namespace.c:4123
do_mount fs/namespace.c:4136 [inline]
__do_sys_mount fs/namespace.c:4347 [inline]
__se_sys_mount fs/namespace.c:4324 [inline]
__x64_sys_mount+0x28d/0x310 fs/namespace.c:4324
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
page last free pid 6026 tgid 6026 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1395 [inline]
__free_frozen_pages+0x7d5/0x10f0 mm/page_alloc.c:2895
discard_slab mm/slub.c:2758 [inline]
__put_partials+0x165/0x1c0 mm/slub.c:3223
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:340
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4191 [inline]
slab_alloc_node mm/slub.c:4240 [inline]
kmem_cache_alloc_noprof+0x1cb/0x3b0 mm/slub.c:4247
vm_area_dup+0x27/0x8d0 mm/vma_init.c:122
__split_vma+0x18e/0x1070 mm/vma.c:515
vms_gather_munmap_vmas+0x1d2/0x1340 mm/vma.c:1359
__mmap_prepare mm/vma.c:2359 [inline]
__mmap_region+0x436/0x27b0 mm/vma.c:2651
mmap_region+0x1ab/0x3f0 mm/vma.c:2739
do_mmap+0xa3e/0x1210 mm/mmap.c:558
vm_mmap_pgoff+0x29e/0x470 mm/util.c:580
ksys_mmap_pgoff+0x32c/0x5c0 mm/mmap.c:604
__do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline]
__se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline]
__x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
Memory state around the buggy address:
ffff88807d7e6d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88807d7e6d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88807d7e6e00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88807d7e6e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807d7e6f00: 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.
next prev parent reply other threads:[~2025-09-21 4:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-29 11:26 [syzbot] [fs?] KASAN: slab-use-after-free Read in driver_remove_file syzbot
2025-09-21 4:04 ` syzbot [this message]
2025-09-21 11:22 ` Edward Adam Davis
2025-09-21 11:40 ` syzbot
2025-09-21 11:55 ` Edward Adam Davis
2025-09-21 12:20 ` syzbot
2025-09-21 12:20 ` [PATCH] comedi: Unregister is prohibited when attach fails before register Edward Adam Davis
2025-09-21 12:38 ` [syzbot] [fs?] KASAN: slab-use-after-free Read in driver_remove_file Hillf Danton
2025-09-21 13:06 ` syzbot
2026-01-05 9:58 ` syzbot
2026-01-06 10:30 ` Forwarded: " syzbot
-- strict thread matches above, loose matches on Subject: below --
2025-09-24 6:31 [syzbot] [fs?] KASAN: slab-use-after-free Read in bus_remove_driver syzbot
2025-09-24 7:22 ` [syzbot] [fs?] KASAN: slab-use-after-free Read in driver_remove_file Edward Adam Davis
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=68cf794c.050a0220.13cd81.002a.GAE@google.com \
--to=syzbot+a56aa983ce6a1bf12485@syzkaller.appspotmail.com \
--cc=dakr@kernel.org \
--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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.