[syzbot] [fuse?] [block?] KASAN: slab-use-after-free Read in disk_add_events

[syzbot] [fuse?] [block?] KASAN: slab-use-after-free Read in disk_add_events

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    ced1b9e0392d Merge tag 'ata-6.17-rc1' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=133b8cf0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=52c12ce9080f644c
dashboard link: https://syzkaller.appspot.com/bug?extid=fa3a12519f0d3fd4ec16
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=154b31bc580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=171a9782580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-ced1b9e0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c709b0d9538c/vmlinux-ced1b9e0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/129af0799fa3/bzImage-ced1b9e0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fa3a12519f0d3fd4ec16@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x151/0x190 lib/list_debug.c:32
Read of size 8 at addr ffff888036fa1400 by task syz.2.1231/9834

CPU: 3 UID: 0 PID: 9834 Comm: syz.2.1231 Not tainted 6.16.0-syzkaller-00857-gced1b9e0392d #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
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
 __list_add_valid_or_report+0x151/0x190 lib/list_debug.c:32
 __list_add_valid include/linux/list.h:88 [inline]
 __list_add include/linux/list.h:150 [inline]
 list_add_tail include/linux/list.h:183 [inline]
 disk_add_events+0x90/0x170 block/disk-events.c:463
 add_disk_final block/genhd.c:427 [inline]
 add_disk_fwnode+0x3c8/0x5d0 block/genhd.c:610
 add_disk include/linux/blkdev.h:773 [inline]
 md_alloc+0x3c2/0x1080 drivers/md/md.c:5981
 md_alloc_and_put drivers/md/md.c:6016 [inline]
 md_probe drivers/md/md.c:6029 [inline]
 md_probe+0x6e/0xd0 drivers/md/md.c:6024
 blk_probe_dev+0x116/0x1a0 block/genhd.c:884
 blk_request_module+0x16/0xb0 block/genhd.c:897
 blkdev_get_no_open+0x9b/0x100 block/bdev.c:825
 blkdev_open+0x141/0x3f0 block/fops.c:684
 do_dentry_open+0x744/0x1c10 fs/open.c:965
 vfs_open+0x82/0x3f0 fs/open.c:1095
 do_open fs/namei.c:3887 [inline]
 path_openat+0x1de4/0x2cb0 fs/namei.c:4046
 do_filp_open+0x20b/0x470 fs/namei.c:4073
 do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
 do_sys_open fs/open.c:1450 [inline]
 __do_sys_openat fs/open.c:1466 [inline]
 __se_sys_openat fs/open.c:1461 [inline]
 __x64_sys_openat+0x174/0x210 fs/open.c:1461
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4ea558e9a9
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:00007f4ea645e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f4ea57b6080 RCX: 00007f4ea558e9a9
RDX: 0000000000000000 RSI: 0000200000000a80 RDI: ffffffffffffff9c
RBP: 00007f4ea5610d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f4ea57b6080 R15: 00007fff25d53038
 </TASK>

Allocated by task 9822:
 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:377 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 disk_alloc_events+0xf0/0x3f0 block/disk-events.c:439
 __add_disk+0x475/0xf00 block/genhd.c:500
 add_disk_fwnode+0x3f8/0x5d0 block/genhd.c:601
 add_disk include/linux/blkdev.h:773 [inline]
 md_alloc+0x3c2/0x1080 drivers/md/md.c:5981
 md_alloc_and_put drivers/md/md.c:6016 [inline]
 md_probe drivers/md/md.c:6029 [inline]
 md_probe+0x6e/0xd0 drivers/md/md.c:6024
 blk_probe_dev+0x116/0x1a0 block/genhd.c:884
 blk_request_module+0x16/0xb0 block/genhd.c:897
 blkdev_get_no_open+0x9b/0x100 block/bdev.c:825
 blkdev_open+0x141/0x3f0 block/fops.c:684
 do_dentry_open+0x744/0x1c10 fs/open.c:965
 vfs_open+0x82/0x3f0 fs/open.c:1095
 do_open fs/namei.c:3887 [inline]
 path_openat+0x1de4/0x2cb0 fs/namei.c:4046
 do_filp_open+0x20b/0x470 fs/namei.c:4073
 do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
 do_sys_open fs/open.c:1450 [inline]
 __do_sys_openat fs/open.c:1466 [inline]
 __se_sys_openat fs/open.c:1461 [inline]
 __x64_sys_openat+0x174/0x210 fs/open.c:1461
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 9817:
 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:247 [inline]
 __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2381 [inline]
 slab_free mm/slub.c:4643 [inline]
 kfree+0x2b4/0x4d0 mm/slub.c:4842
 disk_release+0x161/0x410 block/genhd.c:1301
 device_release+0xa1/0x240 drivers/base/core.c:2568
 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
 put_device+0x1f/0x30 drivers/base/core.c:3800
 blkdev_release+0x15/0x20 block/fops.c:699
 __fput+0x402/0xb70 fs/file_table.c:468
 task_work_run+0x14d/0x240 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xeb/0x110 kernel/entry/common.c:114
 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
 do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888036fa1400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 freed 512-byte region [ffff888036fa1400, ffff888036fa1600)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x36fa0
head: order:2 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 ffff88801b842c80 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b842c80 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000002 ffffea0000dbe801 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 2, tgid 2 (kthreadd), ts 71482349709, free_ts 68765218476
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1704
 prep_new_page mm/page_alloc.c:1712 [inline]
 get_page_from_freelist+0x1321/0x3890 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:4959
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2419
 alloc_slab_page mm/slub.c:2451 [inline]
 allocate_slab mm/slub.c:2619 [inline]
 new_slab+0x23b/0x330 mm/slub.c:2673
 ___slab_alloc+0xd9c/0x1940 mm/slub.c:3859
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3949
 __slab_alloc_node mm/slub.c:4024 [inline]
 slab_alloc_node mm/slub.c:4185 [inline]
 __kmalloc_cache_noprof+0xfb/0x3e0 mm/slub.c:4354
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 set_kthread_struct+0xcb/0x380 kernel/kthread.c:126
 copy_process+0x3107/0x7650 kernel/fork.c:2097
 kernel_clone+0xfc/0x960 kernel/fork.c:2599
 kernel_thread+0xd4/0x120 kernel/fork.c:2661
 create_kthread kernel/kthread.c:487 [inline]
 kthreadd+0x503/0x800 kernel/kthread.c:847
 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 6016 tgid 6016 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 __free_frozen_pages+0x7fe/0x1180 mm/page_alloc.c:2706
 vfree+0x1fd/0xb50 mm/vmalloc.c:3434
 kcov_put kernel/kcov.c:439 [inline]
 kcov_put kernel/kcov.c:435 [inline]
 kcov_close+0x34/0x60 kernel/kcov.c:535
 __fput+0x402/0xb70 fs/file_table.c:468
 task_work_run+0x14d/0x240 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x86c/0x2bd0 kernel/exit.c:964
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
 get_signal+0x2673/0x26d0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x8f/0x7d0 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x84/0x110 kernel/entry/common.c:111
 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
 do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888036fa1300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888036fa1380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888036fa1400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888036fa1480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888036fa1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

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.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

syztest

[Arnaud Lecomte]

#syz test

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5978,10 +5978,6 @@ struct mddev *md_alloc(dev_t dev, char *name)
 
 	disk->events |= DISK_EVENT_MEDIA_CHANGE;
 	mddev->gendisk = disk;
-	error = add_disk(disk);
-	if (error)
-		goto out_put_disk;
-
 	kobject_init(&mddev->kobj, &md_ktype);
 	error = kobject_add(&mddev->kobj, &disk_to_dev(disk)->kobj, "%s", "md");
 	if (error) {
@@ -5999,6 +5995,9 @@ struct mddev *md_alloc(dev_t dev, char *name)
 	kobject_uevent(&mddev->kobj, KOBJ_ADD);
 	mddev->sysfs_state = sysfs_get_dirent_safe(mddev->kobj.sd, "array_state");
 	mddev->sysfs_level = sysfs_get_dirent_safe(mddev->kobj.sd, "level");
+	error = add_disk(disk);
+	if (error)
+		goto out_put_disk;
 	mutex_unlock(&disks_mutex);
 	return mddev;
 
-- 
2.43.0

Re: syztest

[Yu Kuai]

Hi,

在 2025/07/30 13:51, Arnaud Lecomte 写道:
> #syz test
> 
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -5978,10 +5978,6 @@ struct mddev *md_alloc(dev_t dev, char *name)
>   
>   	disk->events |= DISK_EVENT_MEDIA_CHANGE;
>   	mddev->gendisk = disk;
> -	error = add_disk(disk);
> -	if (error)
> -		goto out_put_disk;
> -
>   	kobject_init(&mddev->kobj, &md_ktype);
>   	error = kobject_add(&mddev->kobj, &disk_to_dev(disk)->kobj, "%s", "md");

This is wrong, you can't add mddev >kobj under the disk without
kobject_add for the disk kobj.

Thanks,
Kuai

>   	if (error) {
> @@ -5999,6 +5995,9 @@ struct mddev *md_alloc(dev_t dev, char *name)
>   	kobject_uevent(&mddev->kobj, KOBJ_ADD);
>   	mddev->sysfs_state = sysfs_get_dirent_safe(mddev->kobj.sd, "array_state");
>   	mddev->sysfs_level = sysfs_get_dirent_safe(mddev->kobj.sd, "level");
> +	error = add_disk(disk);
> +	if (error)
> +		goto out_put_disk;
>   	mutex_unlock(&disks_mutex);
>   	return mddev;
>   
> 

Re: syztest

[Arnaud Lecomte]

On 30/07/2025 07:09, Yu Kuai wrote:
> Hi,
>
> 在 2025/07/30 13:51, Arnaud Lecomte 写道:
>> #syz test
>>
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -5978,10 +5978,6 @@ struct mddev *md_alloc(dev_t dev, char *name)
>>         disk->events |= DISK_EVENT_MEDIA_CHANGE;
>>       mddev->gendisk = disk;
>> -    error = add_disk(disk);
>> -    if (error)
>> -        goto out_put_disk;
>> -
>>       kobject_init(&mddev->kobj, &md_ktype);
>>       error = kobject_add(&mddev->kobj, &disk_to_dev(disk)->kobj, 
>> "%s", "md");
>
> This is wrong, you can't add mddev >kobj under the disk without
> kobject_add for the disk kobj.
>
Will dive a bit more into that after work,
Thanks

> Thanks,
> Kuai
>
>>       if (error) {
>> @@ -5999,6 +5995,9 @@ struct mddev *md_alloc(dev_t dev, char *name)
>>       kobject_uevent(&mddev->kobj, KOBJ_ADD);
>>       mddev->sysfs_state = sysfs_get_dirent_safe(mddev->kobj.sd, 
>> "array_state");
>>       mddev->sysfs_level = sysfs_get_dirent_safe(mddev->kobj.sd, 
>> "level");
>> +    error = add_disk(disk);
>> +    if (error)
>> +        goto out_put_disk;
>>       mutex_unlock(&disks_mutex);
>>       return mddev;
>>
>

Re: [syzbot] [fuse?] [block?] KASAN: slab-use-after-free Read in disk_add_events

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+fa3a12519f0d3fd4ec16@syzkaller.appspotmail.com
Tested-by: syzbot+fa3a12519f0d3fd4ec16@syzkaller.appspotmail.com

Tested on:

commit:         4b290aae Merge tag 'sysctl-6.17-rc1' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10908834580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=295b41325f4e1bab
dashboard link: https://syzkaller.appspot.com/bug?extid=fa3a12519f0d3fd4ec16
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=15ac34a2580000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [fuse?] [block?] KASAN: slab-use-after-free Read in disk_add_events

[Yu Kuai]

+CC Xiao

在 2025/07/30 5:58, syzbot 写道:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    ced1b9e0392d Merge tag 'ata-6.17-rc1' of git://git.kernel...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=133b8cf0580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=52c12ce9080f644c
> dashboard link: https://syzkaller.appspot.com/bug?extid=fa3a12519f0d3fd4ec16
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=154b31bc580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=171a9782580000
> 

This looks like the same cause with another report:

https://lore.kernel.org/all/68894408.a00a0220.26d0e1.0012.GAE@google.com/

The mddev kobject liftime is broken, now in the case del_work is queued,
means mddev is about to be freed, meanwhile md_open can succeed.

Thanks,
Kuai

> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-ced1b9e0.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/c709b0d9538c/vmlinux-ced1b9e0.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/129af0799fa3/bzImage-ced1b9e0.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+fa3a12519f0d3fd4ec16@syzkaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x151/0x190 lib/list_debug.c:32
> Read of size 8 at addr ffff888036fa1400 by task syz.2.1231/9834
> 
> CPU: 3 UID: 0 PID: 9834 Comm: syz.2.1231 Not tainted 6.16.0-syzkaller-00857-gced1b9e0392d #0 PREEMPT(full)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> 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
>   __list_add_valid_or_report+0x151/0x190 lib/list_debug.c:32
>   __list_add_valid include/linux/list.h:88 [inline]
>   __list_add include/linux/list.h:150 [inline]
>   list_add_tail include/linux/list.h:183 [inline]
>   disk_add_events+0x90/0x170 block/disk-events.c:463
>   add_disk_final block/genhd.c:427 [inline]
>   add_disk_fwnode+0x3c8/0x5d0 block/genhd.c:610
>   add_disk include/linux/blkdev.h:773 [inline]
>   md_alloc+0x3c2/0x1080 drivers/md/md.c:5981
>   md_alloc_and_put drivers/md/md.c:6016 [inline]
>   md_probe drivers/md/md.c:6029 [inline]
>   md_probe+0x6e/0xd0 drivers/md/md.c:6024
>   blk_probe_dev+0x116/0x1a0 block/genhd.c:884
>   blk_request_module+0x16/0xb0 block/genhd.c:897
>   blkdev_get_no_open+0x9b/0x100 block/bdev.c:825
>   blkdev_open+0x141/0x3f0 block/fops.c:684
>   do_dentry_open+0x744/0x1c10 fs/open.c:965
>   vfs_open+0x82/0x3f0 fs/open.c:1095
>   do_open fs/namei.c:3887 [inline]
>   path_openat+0x1de4/0x2cb0 fs/namei.c:4046
>   do_filp_open+0x20b/0x470 fs/namei.c:4073
>   do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
>   do_sys_open fs/open.c:1450 [inline]
>   __do_sys_openat fs/open.c:1466 [inline]
>   __se_sys_openat fs/open.c:1461 [inline]
>   __x64_sys_openat+0x174/0x210 fs/open.c:1461
>   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>   do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f4ea558e9a9
> 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:00007f4ea645e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
> RAX: ffffffffffffffda RBX: 00007f4ea57b6080 RCX: 00007f4ea558e9a9
> RDX: 0000000000000000 RSI: 0000200000000a80 RDI: ffffffffffffff9c
> RBP: 00007f4ea5610d69 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 00007f4ea57b6080 R15: 00007fff25d53038
>   </TASK>
> 
> Allocated by task 9822:
>   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:377 [inline]
>   __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
>   kmalloc_noprof include/linux/slab.h:905 [inline]
>   kzalloc_noprof include/linux/slab.h:1039 [inline]
>   disk_alloc_events+0xf0/0x3f0 block/disk-events.c:439
>   __add_disk+0x475/0xf00 block/genhd.c:500
>   add_disk_fwnode+0x3f8/0x5d0 block/genhd.c:601
>   add_disk include/linux/blkdev.h:773 [inline]
>   md_alloc+0x3c2/0x1080 drivers/md/md.c:5981
>   md_alloc_and_put drivers/md/md.c:6016 [inline]
>   md_probe drivers/md/md.c:6029 [inline]
>   md_probe+0x6e/0xd0 drivers/md/md.c:6024
>   blk_probe_dev+0x116/0x1a0 block/genhd.c:884
>   blk_request_module+0x16/0xb0 block/genhd.c:897
>   blkdev_get_no_open+0x9b/0x100 block/bdev.c:825
>   blkdev_open+0x141/0x3f0 block/fops.c:684
>   do_dentry_open+0x744/0x1c10 fs/open.c:965
>   vfs_open+0x82/0x3f0 fs/open.c:1095
>   do_open fs/namei.c:3887 [inline]
>   path_openat+0x1de4/0x2cb0 fs/namei.c:4046
>   do_filp_open+0x20b/0x470 fs/namei.c:4073
>   do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
>   do_sys_open fs/open.c:1450 [inline]
>   __do_sys_openat fs/open.c:1466 [inline]
>   __se_sys_openat fs/open.c:1461 [inline]
>   __x64_sys_openat+0x174/0x210 fs/open.c:1461
>   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>   do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Freed by task 9817:
>   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:247 [inline]
>   __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
>   kasan_slab_free include/linux/kasan.h:233 [inline]
>   slab_free_hook mm/slub.c:2381 [inline]
>   slab_free mm/slub.c:4643 [inline]
>   kfree+0x2b4/0x4d0 mm/slub.c:4842
>   disk_release+0x161/0x410 block/genhd.c:1301
>   device_release+0xa1/0x240 drivers/base/core.c:2568
>   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
>   put_device+0x1f/0x30 drivers/base/core.c:3800
>   blkdev_release+0x15/0x20 block/fops.c:699
>   __fput+0x402/0xb70 fs/file_table.c:468
>   task_work_run+0x14d/0x240 kernel/task_work.c:227
>   resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
>   exit_to_user_mode_loop+0xeb/0x110 kernel/entry/common.c:114
>   exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
>   syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
>   syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
>   do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> The buggy address belongs to the object at ffff888036fa1400
>   which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 0 bytes inside of
>   freed 512-byte region [ffff888036fa1400, ffff888036fa1600)
> 
> The buggy address belongs to the physical page:
> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x36fa0
> head: order:2 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 ffff88801b842c80 dead000000000100 dead000000000122
> raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
> head: 00fff00000000040 ffff88801b842c80 dead000000000100 dead000000000122
> head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
> head: 00fff00000000002 ffffea0000dbe801 00000000ffffffff 00000000ffffffff
> head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 2, tgid 2 (kthreadd), ts 71482349709, free_ts 68765218476
>   set_page_owner include/linux/page_owner.h:32 [inline]
>   post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1704
>   prep_new_page mm/page_alloc.c:1712 [inline]
>   get_page_from_freelist+0x1321/0x3890 mm/page_alloc.c:3669
>   __alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:4959
>   alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2419
>   alloc_slab_page mm/slub.c:2451 [inline]
>   allocate_slab mm/slub.c:2619 [inline]
>   new_slab+0x23b/0x330 mm/slub.c:2673
>   ___slab_alloc+0xd9c/0x1940 mm/slub.c:3859
>   __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3949
>   __slab_alloc_node mm/slub.c:4024 [inline]
>   slab_alloc_node mm/slub.c:4185 [inline]
>   __kmalloc_cache_noprof+0xfb/0x3e0 mm/slub.c:4354
>   kmalloc_noprof include/linux/slab.h:905 [inline]
>   kzalloc_noprof include/linux/slab.h:1039 [inline]
>   set_kthread_struct+0xcb/0x380 kernel/kthread.c:126
>   copy_process+0x3107/0x7650 kernel/fork.c:2097
>   kernel_clone+0xfc/0x960 kernel/fork.c:2599
>   kernel_thread+0xd4/0x120 kernel/fork.c:2661
>   create_kthread kernel/kthread.c:487 [inline]
>   kthreadd+0x503/0x800 kernel/kthread.c:847
>   ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
>   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> page last free pid 6016 tgid 6016 stack trace:
>   reset_page_owner include/linux/page_owner.h:25 [inline]
>   free_pages_prepare mm/page_alloc.c:1248 [inline]
>   __free_frozen_pages+0x7fe/0x1180 mm/page_alloc.c:2706
>   vfree+0x1fd/0xb50 mm/vmalloc.c:3434
>   kcov_put kernel/kcov.c:439 [inline]
>   kcov_put kernel/kcov.c:435 [inline]
>   kcov_close+0x34/0x60 kernel/kcov.c:535
>   __fput+0x402/0xb70 fs/file_table.c:468
>   task_work_run+0x14d/0x240 kernel/task_work.c:227
>   exit_task_work include/linux/task_work.h:40 [inline]
>   do_exit+0x86c/0x2bd0 kernel/exit.c:964
>   do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
>   get_signal+0x2673/0x26d0 kernel/signal.c:3034
>   arch_do_signal_or_restart+0x8f/0x7d0 arch/x86/kernel/signal.c:337
>   exit_to_user_mode_loop+0x84/0x110 kernel/entry/common.c:111
>   exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
>   syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
>   syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
>   do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Memory state around the buggy address:
>   ffff888036fa1300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>   ffff888036fa1380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> ffff888036fa1400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                     ^
>   ffff888036fa1480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff888036fa1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> 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.
> 
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup
> 
> 
> .
> 

Re: [syzbot] [fuse?] [block?] KASAN: slab-use-after-free Read in disk_add_events

[Yu Kuai]

在 2025/07/30 14:14, Yu Kuai 写道:
> +CC Xiao

Forgot to CC in the last emial, sorry for the noisy.

Thanks,
Kuai

> 
> 在 2025/07/30 5:58, syzbot 写道:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    ced1b9e0392d Merge tag 'ata-6.17-rc1' of 
>> git://git.kernel...
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=133b8cf0580000
>> kernel config:  
>> https://syzkaller.appspot.com/x/.config?x=52c12ce9080f644c
>> dashboard link: 
>> https://syzkaller.appspot.com/bug?extid=fa3a12519f0d3fd4ec16
>> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils 
>> for Debian) 2.40
>> syz repro:      
>> https://syzkaller.appspot.com/x/repro.syz?x=154b31bc580000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=171a9782580000
>>
> 
> This looks like the same cause with another report:
> 
> https://lore.kernel.org/all/68894408.a00a0220.26d0e1.0012.GAE@google.com/
> 
> The mddev kobject liftime is broken, now in the case del_work is queued,
> means mddev is about to be freed, meanwhile md_open can succeed.
> 
> Thanks,
> Kuai
> 
>> Downloadable assets:
>> disk image (non-bootable): 
>> https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-ced1b9e0.raw.xz 
>>
>> vmlinux: 
>> https://storage.googleapis.com/syzbot-assets/c709b0d9538c/vmlinux-ced1b9e0.xz 
>>
>> kernel image: 
>> https://storage.googleapis.com/syzbot-assets/129af0799fa3/bzImage-ced1b9e0.xz 
>>
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the 
>> commit:
>> Reported-by: syzbot+fa3a12519f0d3fd4ec16@syzkaller.appspotmail.com
>>
>> ==================================================================
>> BUG: KASAN: slab-use-after-free in 
>> __list_add_valid_or_report+0x151/0x190 lib/list_debug.c:32
>> Read of size 8 at addr ffff888036fa1400 by task syz.2.1231/9834
>>
>> CPU: 3 UID: 0 PID: 9834 Comm: syz.2.1231 Not tainted 
>> 6.16.0-syzkaller-00857-gced1b9e0392d #0 PREEMPT(full)
>> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 
>> 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
>> 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
>>   __list_add_valid_or_report+0x151/0x190 lib/list_debug.c:32
>>   __list_add_valid include/linux/list.h:88 [inline]
>>   __list_add include/linux/list.h:150 [inline]
>>   list_add_tail include/linux/list.h:183 [inline]
>>   disk_add_events+0x90/0x170 block/disk-events.c:463
>>   add_disk_final block/genhd.c:427 [inline]
>>   add_disk_fwnode+0x3c8/0x5d0 block/genhd.c:610
>>   add_disk include/linux/blkdev.h:773 [inline]
>>   md_alloc+0x3c2/0x1080 drivers/md/md.c:5981
>>   md_alloc_and_put drivers/md/md.c:6016 [inline]
>>   md_probe drivers/md/md.c:6029 [inline]
>>   md_probe+0x6e/0xd0 drivers/md/md.c:6024
>>   blk_probe_dev+0x116/0x1a0 block/genhd.c:884
>>   blk_request_module+0x16/0xb0 block/genhd.c:897
>>   blkdev_get_no_open+0x9b/0x100 block/bdev.c:825
>>   blkdev_open+0x141/0x3f0 block/fops.c:684
>>   do_dentry_open+0x744/0x1c10 fs/open.c:965
>>   vfs_open+0x82/0x3f0 fs/open.c:1095
>>   do_open fs/namei.c:3887 [inline]
>>   path_openat+0x1de4/0x2cb0 fs/namei.c:4046
>>   do_filp_open+0x20b/0x470 fs/namei.c:4073
>>   do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
>>   do_sys_open fs/open.c:1450 [inline]
>>   __do_sys_openat fs/open.c:1466 [inline]
>>   __se_sys_openat fs/open.c:1461 [inline]
>>   __x64_sys_openat+0x174/0x210 fs/open.c:1461
>>   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>>   do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
>>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> RIP: 0033:0x7f4ea558e9a9
>> 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:00007f4ea645e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
>> RAX: ffffffffffffffda RBX: 00007f4ea57b6080 RCX: 00007f4ea558e9a9
>> RDX: 0000000000000000 RSI: 0000200000000a80 RDI: ffffffffffffff9c
>> RBP: 00007f4ea5610d69 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
>> R13: 0000000000000000 R14: 00007f4ea57b6080 R15: 00007fff25d53038
>>   </TASK>
>>
>> Allocated by task 9822:
>>   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:377 [inline]
>>   __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
>>   kmalloc_noprof include/linux/slab.h:905 [inline]
>>   kzalloc_noprof include/linux/slab.h:1039 [inline]
>>   disk_alloc_events+0xf0/0x3f0 block/disk-events.c:439
>>   __add_disk+0x475/0xf00 block/genhd.c:500
>>   add_disk_fwnode+0x3f8/0x5d0 block/genhd.c:601
>>   add_disk include/linux/blkdev.h:773 [inline]
>>   md_alloc+0x3c2/0x1080 drivers/md/md.c:5981
>>   md_alloc_and_put drivers/md/md.c:6016 [inline]
>>   md_probe drivers/md/md.c:6029 [inline]
>>   md_probe+0x6e/0xd0 drivers/md/md.c:6024
>>   blk_probe_dev+0x116/0x1a0 block/genhd.c:884
>>   blk_request_module+0x16/0xb0 block/genhd.c:897
>>   blkdev_get_no_open+0x9b/0x100 block/bdev.c:825
>>   blkdev_open+0x141/0x3f0 block/fops.c:684
>>   do_dentry_open+0x744/0x1c10 fs/open.c:965
>>   vfs_open+0x82/0x3f0 fs/open.c:1095
>>   do_open fs/namei.c:3887 [inline]
>>   path_openat+0x1de4/0x2cb0 fs/namei.c:4046
>>   do_filp_open+0x20b/0x470 fs/namei.c:4073
>>   do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
>>   do_sys_open fs/open.c:1450 [inline]
>>   __do_sys_openat fs/open.c:1466 [inline]
>>   __se_sys_openat fs/open.c:1461 [inline]
>>   __x64_sys_openat+0x174/0x210 fs/open.c:1461
>>   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>>   do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
>>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
>>
>> Freed by task 9817:
>>   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:247 [inline]
>>   __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
>>   kasan_slab_free include/linux/kasan.h:233 [inline]
>>   slab_free_hook mm/slub.c:2381 [inline]
>>   slab_free mm/slub.c:4643 [inline]
>>   kfree+0x2b4/0x4d0 mm/slub.c:4842
>>   disk_release+0x161/0x410 block/genhd.c:1301
>>   device_release+0xa1/0x240 drivers/base/core.c:2568
>>   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
>>   put_device+0x1f/0x30 drivers/base/core.c:3800
>>   blkdev_release+0x15/0x20 block/fops.c:699
>>   __fput+0x402/0xb70 fs/file_table.c:468
>>   task_work_run+0x14d/0x240 kernel/task_work.c:227
>>   resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
>>   exit_to_user_mode_loop+0xeb/0x110 kernel/entry/common.c:114
>>   exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
>>   syscall_exit_to_user_mode_work include/linux/entry-common.h:414 
>> [inline]
>>   syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
>>   do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100
>>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
>>
>> The buggy address belongs to the object at ffff888036fa1400
>>   which belongs to the cache kmalloc-512 of size 512
>> The buggy address is located 0 bytes inside of
>>   freed 512-byte region [ffff888036fa1400, ffff888036fa1600)
>>
>> The buggy address belongs to the physical page:
>> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 
>> pfn:0x36fa0
>> head: order:2 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 ffff88801b842c80 dead000000000100 dead000000000122
>> raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
>> head: 00fff00000000040 ffff88801b842c80 dead000000000100 dead000000000122
>> head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
>> head: 00fff00000000002 ffffea0000dbe801 00000000ffffffff 00000000ffffffff
>> head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
>> page dumped because: kasan: bad access detected
>> page_owner tracks the page as allocated
>> page last allocated via order 2, migratetype Unmovable, gfp_mask 
>> 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), 
>> pid 2, tgid 2 (kthreadd), ts 71482349709, free_ts 68765218476
>>   set_page_owner include/linux/page_owner.h:32 [inline]
>>   post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1704
>>   prep_new_page mm/page_alloc.c:1712 [inline]
>>   get_page_from_freelist+0x1321/0x3890 mm/page_alloc.c:3669
>>   __alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:4959
>>   alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2419
>>   alloc_slab_page mm/slub.c:2451 [inline]
>>   allocate_slab mm/slub.c:2619 [inline]
>>   new_slab+0x23b/0x330 mm/slub.c:2673
>>   ___slab_alloc+0xd9c/0x1940 mm/slub.c:3859
>>   __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3949
>>   __slab_alloc_node mm/slub.c:4024 [inline]
>>   slab_alloc_node mm/slub.c:4185 [inline]
>>   __kmalloc_cache_noprof+0xfb/0x3e0 mm/slub.c:4354
>>   kmalloc_noprof include/linux/slab.h:905 [inline]
>>   kzalloc_noprof include/linux/slab.h:1039 [inline]
>>   set_kthread_struct+0xcb/0x380 kernel/kthread.c:126
>>   copy_process+0x3107/0x7650 kernel/fork.c:2097
>>   kernel_clone+0xfc/0x960 kernel/fork.c:2599
>>   kernel_thread+0xd4/0x120 kernel/fork.c:2661
>>   create_kthread kernel/kthread.c:487 [inline]
>>   kthreadd+0x503/0x800 kernel/kthread.c:847
>>   ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
>>   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>> page last free pid 6016 tgid 6016 stack trace:
>>   reset_page_owner include/linux/page_owner.h:25 [inline]
>>   free_pages_prepare mm/page_alloc.c:1248 [inline]
>>   __free_frozen_pages+0x7fe/0x1180 mm/page_alloc.c:2706
>>   vfree+0x1fd/0xb50 mm/vmalloc.c:3434
>>   kcov_put kernel/kcov.c:439 [inline]
>>   kcov_put kernel/kcov.c:435 [inline]
>>   kcov_close+0x34/0x60 kernel/kcov.c:535
>>   __fput+0x402/0xb70 fs/file_table.c:468
>>   task_work_run+0x14d/0x240 kernel/task_work.c:227
>>   exit_task_work include/linux/task_work.h:40 [inline]
>>   do_exit+0x86c/0x2bd0 kernel/exit.c:964
>>   do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
>>   get_signal+0x2673/0x26d0 kernel/signal.c:3034
>>   arch_do_signal_or_restart+0x8f/0x7d0 arch/x86/kernel/signal.c:337
>>   exit_to_user_mode_loop+0x84/0x110 kernel/entry/common.c:111
>>   exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
>>   syscall_exit_to_user_mode_work include/linux/entry-common.h:414 
>> [inline]
>>   syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
>>   do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100
>>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
>>
>> Memory state around the buggy address:
>>   ffff888036fa1300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>   ffff888036fa1380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>> ffff888036fa1400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>                     ^
>>   ffff888036fa1480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>   ffff888036fa1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ==================================================================
>>
>>
>> ---
>> This report is generated by a bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for more information about syzbot.
>> syzbot engineers can be reached at syzkaller@googlegroups.com.
>>
>> syzbot will keep track of this issue. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>>
>> If the report is already addressed, let syzbot know by replying with:
>> #syz fix: exact-commit-title
>>
>> 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.
>>
>> If you want to overwrite report's subsystems, reply with:
>> #syz set subsystems: new-subsystem
>> (See the list of subsystem names on the web dashboard)
>>
>> If the report is a duplicate of another one, reply with:
>> #syz dup: exact-subject-of-another-report
>>
>> If you want to undo deduplication, reply with:
>> #syz undup
>>
>>
>> .
>>
> 
> .
> 

[syzbot] [block?] BUG: unable to handle kernel NULL pointer dereference in guard_bio_eod

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    6fea5fabd332 Merge tag 'mm-hotfixes-stable-2025-04-19-21-2..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15551ccc580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b7c08f42e927242f
dashboard link: https://syzkaller.appspot.com/bug?extid=3291296495fc970e4b1c
compiler:       aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17551ccc580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13a7f4cc580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/384ffdcca292/non_bootable_disk-6fea5fab.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/59473b9bbb43/vmlinux-6fea5fab.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a2e0095d3721/Image-6fea5fab.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3291296495fc970e4b1c@syzkaller.appspotmail.com

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
Mem abort info:
  ESR = 0x0000000096000006
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x06: level 2 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000
  CM = 0, WnR = 0, TnD = 0, TagAccess = 0
  GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
user pgtable: 4k pages, 52-bit VAs, pgdp=00000000442aa200
[0000000000000008] pgd=080000004b293403, p4d=080000004b27f403, pud=080000004b237403, pmd=0000000000000000
Internal error: Oops: 0000000096000006 [#1]  SMP
Modules linked in:
CPU: 1 UID: 0 PID: 6338 Comm: syz-executor150 Not tainted 6.15.0-rc2-syzkaller-00488-g6fea5fabd332 #0 PREEMPT 
Hardware name: linux,dummy-virt (DT)
pstate: 41402009 (nZcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
pc : bdev_nr_sectors include/linux/blkdev.h:831 [inline]
pc : guard_bio_eod+0x18/0x210 block/bio.c:694
lr : mpage_bio_submit_read fs/mpage.c:74 [inline]
lr : do_mpage_readpage+0x2d0/0x6dc fs/mpage.c:296
sp : ffff80008331b820
x29: ffff80008331b820 x28: f4f0000004143e00 x27: ffff80008331b960
x26: 0000000000000001 x25: ffff80008331b940 x24: 0000000000000000
x23: 0000000000000000 x22: 0000000000000000 x21: ffffc1ffc02c9dc0
x20: 0000000000000010 x19: f4f0000004143e00 x18: 0000000000001000
x17: 0000000000000000 x16: 1e9e000000c6abc1 x15: 0000000000000000
x14: ffffc1ffc02c9dc0 x13: 0000000000000000 x12: f4f0000004143e00
x11: 0000000000000000 x10: ffffc1ffc02ca580 x9 : 0000000000000003
x8 : 00000000000000b8 x7 : fcf0000003f3b97c x6 : f6f0000006355c00
x5 : f6f0000006355c00 x4 : 0000000000000000 x3 : 0000000000000000
x2 : 0000000000000000 x1 : ffff8000803bbfc0 x0 : 0000000000000000
Call trace:
 bdev_nr_sectors include/linux/blkdev.h:831 [inline] (P)
 guard_bio_eod+0x18/0x210 block/bio.c:694 (P)
 mpage_bio_submit_read fs/mpage.c:74 [inline]
 do_mpage_readpage+0x2d0/0x6dc fs/mpage.c:296
 mpage_readahead+0xcc/0x164 fs/mpage.c:371
 blkdev_readahead+0x18/0x24 block/fops.c:472
 read_pages+0x70/0x2b8 mm/readahead.c:160
 page_cache_ra_unbounded+0x1d4/0x260 mm/readahead.c:280
 do_page_cache_ra mm/readahead.c:327 [inline]
 page_cache_ra_order+0x34c/0x400 mm/readahead.c:532
 do_sync_mmap_readahead mm/filemap.c:3262 [inline]
 filemap_fault+0x444/0x924 mm/filemap.c:3403
 __do_fault+0x3c/0x21c mm/memory.c:5098
 do_shared_fault mm/memory.c:5582 [inline]
 do_fault mm/memory.c:5656 [inline]
 do_pte_missing mm/memory.c:4160 [inline]
 handle_pte_fault mm/memory.c:5997 [inline]
 __handle_mm_fault+0xadc/0x1b00 mm/memory.c:6140
 handle_mm_fault+0x164/0x314 mm/memory.c:6309
 do_page_fault+0x118/0x688 arch/arm64/mm/fault.c:647
 do_translation_fault+0xac/0xbc arch/arm64/mm/fault.c:783
 do_mem_abort+0x44/0x94 arch/arm64/mm/fault.c:919
 el0_da+0x78/0xa8 arch/arm64/kernel/entry-common.c:604
 el0t_64_sync_handler+0xc4/0x138 arch/arm64/kernel/entry-common.c:765
 el0t_64_sync+0x1a4/0x1a8 arch/arm64/kernel/entry.S:600
Code: 910003fd a90153f3 aa0003f3 f9400400 (f9400400) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	910003fd 	mov	x29, sp
   4:	a90153f3 	stp	x19, x20, [sp, #16]
   8:	aa0003f3 	mov	x19, x0
   c:	f9400400 	ldr	x0, [x0, #8]
* 10:	f9400400 	ldr	x0, [x0, #8] <-- trapping instruction


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

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.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

syztest

[Arnaud Lecomte]

#syz test

--- a/block/bio.c
+++ b/block/bio.c
@@ -691,6 +691,9 @@ static void bio_truncate(struct bio *bio, unsigned new_size)
  */
 void guard_bio_eod(struct bio *bio)
 {
+	if (unlikely(!bio->bi_bdev)
+		return;
+
 	sector_t maxsector = bdev_nr_sectors(bio->bi_bdev);
 
 	if (!maxsector)
-- 
2.43.0

syztest

[Arnaud Lecomte]

#syz test

--- a/block/bio.c
+++ b/block/bio.c
@@ -691,6 +691,9 @@ static void bio_truncate(struct bio *bio, unsigned new_size)
  */
 void guard_bio_eod(struct bio *bio)
 {
+	if (unlikely(!bio->bi_bdev))
+		return;
+
 	sector_t maxsector = bdev_nr_sectors(bio->bi_bdev);
 
 	if (!maxsector)
-- 
2.43.0