Message-ID: <689cef52.050a0220.7f033.015e.GAE@google.com>
Date: Wed, 13 Aug 2025 13:02:26 -0700
From: syzbot <syzbot+64b38a1abee64ab9246e@...kaller.appspotmail.com>
To: axboe@...nel.dk, linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [block?] KASAN: slab-use-after-free Read in update_io_ticks (3)

Hello,

syzbot found the following issue on:

HEAD commit:    c30a13538d9f Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1044d434580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e143c1cd9dadd720
dashboard link: https://syzkaller.appspot.com/bug?extid=64b38a1abee64ab9246e
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-c30a1353.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8cefa7e1536e/vmlinux-c30a1353.xz
kernel image: https://storage.googleapis.com/syzbot-assets/68b8ee3da77f/bzImage-c30a1353.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+64b38a1abee64ab9246e@...kaller.appspotmail.com

I/O error, dev loop0, sector 2424 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
==================================================================
BUG: KASAN: slab-use-after-free in update_io_ticks+0x9a/0x260 block/blk-core.c:1018
Read of size 8 at addr ffff88803215e7a8 by task kworker/u4:11/3027

CPU: 0 UID: 0 PID: 3027 Comm: kworker/u4:11 Not tainted 6.16.0-syzkaller-12250-gc30a13538d9f #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
Workqueue: loop0 loop_workfn
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 update_io_ticks+0x9a/0x260 block/blk-core.c:1018
 blk_account_io_done+0x19b/0x780 block/blk-mq.c:1055
 __blk_mq_end_request_acct block/blk-mq.c:1129 [inline]
 __blk_mq_end_request+0x2af/0x600 block/blk-mq.c:1135
 lo_rw_aio_complete drivers/block/loop.c:327 [inline]
 lo_rw_aio+0xd75/0xfa0 drivers/block/loop.c:401
 do_req_filebacked drivers/block/loop.c:-1 [inline]
 loop_handle_cmd drivers/block/loop.c:1910 [inline]
 loop_process_work+0x835/0xf90 drivers/block/loop.c:1945
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 5362:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 unpoison_slab_object mm/kasan/common.c:330 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:356
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4180 [inline]
 slab_alloc_node mm/slub.c:4229 [inline]
 kmem_cache_alloc_lru_noprof+0x1c6/0x3d0 mm/slub.c:4248
 bdev_alloc_inode+0x29/0x90 block/bdev.c:364
 alloc_inode+0x67/0x1b0 fs/inode.c:346
 new_inode+0x22/0x170 fs/inode.c:1145
 bdev_alloc+0x26/0x380 block/bdev.c:461
 add_partition+0x1c3/0x8e0 block/partitions/core.c:326
 blk_add_partition block/partitions/core.c:564 [inline]
 blk_add_partitions block/partitions/core.c:633 [inline]
 bdev_disk_changed+0xb50/0x14b0 block/partitions/core.c:693
 loop_reread_partitions drivers/block/loop.c:439 [inline]
 loop_set_status+0x85a/0xb40 drivers/block/loop.c:1265
 lo_ioctl+0x9af/0x1d00 drivers/block/loop.c:-1
 blkdev_ioctl+0x5a8/0x6d0 block/ioctl.c:705
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 15:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:243 [inline]
 __kasan_slab_free+0x5b/0x80 mm/kasan/common.c:275
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2417 [inline]
 slab_free mm/slub.c:4680 [inline]
 kmem_cache_free+0x18f/0x400 mm/slub.c:4782
 rcu_do_batch kernel/rcu/tree.c:2605 [inline]
 rcu_core+0xca8/0x1770 kernel/rcu/tree.c:2861
 handle_softirqs+0x283/0x870 kernel/softirq.c:579
 run_ksoftirqd+0x9b/0x100 kernel/softirq.c:968
 smpboot_thread_fn+0x53f/0xa60 kernel/smpboot.c:160
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:47
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:548
 __call_rcu_common kernel/rcu/tree.c:3123 [inline]
 call_rcu+0x157/0x9c0 kernel/rcu/tree.c:3243
 destroy_inode fs/inode.c:401 [inline]
 evict+0x847/0x9c0 fs/inode.c:834
 device_release+0x99/0x1c0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x22b/0x480 lib/kobject.c:737
 blkdev_release+0x15/0x20 block/fops.c:699
 __fput+0x449/0xa70 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xec/0x110 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88803215e780
 which belongs to the cache bdev_cache of size 2792
The buggy address is located 40 bytes inside of
 freed 2792-byte region [ffff88803215e780, ffff88803215f268)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x32158
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888052e26701
flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000040 ffff88801bed7280 dead000000000122 0000000000000000
raw: 0000000000000000 00000000800b000b 00000000f5000000 ffff888052e26701
head: 04fff00000000040 ffff88801bed7280 dead000000000122 0000000000000000
head: 0000000000000000 00000000800b000b 00000000f5000000 ffff888052e26701
head: 04fff00000000003 ffffea0000c85601 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 Reclaimable, gfp_mask 0xd20d0(__GFP_RECLAIMABLE|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 11814848371, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3858
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5148
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:2487 [inline]
 allocate_slab+0x8a/0x370 mm/slub.c:2655
 new_slab mm/slub.c:2709 [inline]
 ___slab_alloc+0xbeb/0x1410 mm/slub.c:3891
 __slab_alloc mm/slub.c:3981 [inline]
 __slab_alloc_node mm/slub.c:4056 [inline]
 slab_alloc_node mm/slub.c:4217 [inline]
 kmem_cache_alloc_lru_noprof+0x288/0x3d0 mm/slub.c:4248
 bdev_alloc_inode+0x29/0x90 block/bdev.c:364
 alloc_inode+0x67/0x1b0 fs/inode.c:346
 new_inode+0x22/0x170 fs/inode.c:1145
 bdev_alloc+0x26/0x380 block/bdev.c:461
 __alloc_disk_node+0x11c/0x540 block/genhd.c:1464
 __blk_mq_alloc_disk+0x196/0x340 block/blk-mq.c:4451
 nbd_dev_add+0x46c/0xae0 drivers/block/nbd.c:1943
 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2680
 do_one_initcall+0x233/0x820 init/main.c:1269
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88803215e680: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
 ffff88803215e700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88803215e780: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88803215e800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803215e880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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