Forwarded: Re: [syzbot] [io-uring?] KASAN: slab-use-after-free Read in io_poll_remove_entries (2)

[syzbot <syzbot+721cddf316143353975e@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Re: [syzbot] [io-uring?] KASAN: slab-use-after-free Read in io_poll_remove_entries (2)
Author: axboe@kernel.dk

#syz invalid

On Fri, Nov 28, 2025 at 2:02 AM syzbot
<syzbot+721cddf316143353975e@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    ef68bf704646 Add linux-next specific files for 20251127
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=113a9e92580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=75e4ba9be1d3d04
> dashboard link: https://syzkaller.appspot.com/bug?extid=721cddf316143353975e
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/d2c8379aac84/disk-ef68bf70.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/c5f8945ec4ba/vmlinux-ef68bf70.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/dab0de6e99a6/bzImage-ef68bf70.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+721cddf316143353975e@syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
> BUG: KASAN: slab-use-after-free in _raw_spin_lock_irq+0xa2/0xf0 kernel/locking/spinlock.c:170
> Read of size 1 at addr ffff88801c7f2d50 by task kworker/0:8/5987
>
> CPU: 0 UID: 0 PID: 5987 Comm: kworker/0:8 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
> Workqueue: events io_fallback_req_func
> 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
>  __kasan_check_byte+0x2a/0x40 mm/kasan/common.c:573
>  kasan_check_byte include/linux/kasan.h:401 [inline]
>  lock_acquire+0x84/0x340 kernel/locking/lockdep.c:5842
>  __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
>  _raw_spin_lock_irq+0xa2/0xf0 kernel/locking/spinlock.c:170
>  spin_lock_irq include/linux/spinlock.h:376 [inline]
>  io_poll_remove_entry io_uring/poll.c:146 [inline]
>  io_poll_remove_entries+0x1eb/0x620 io_uring/poll.c:179
>  io_poll_task_func+0x6f6/0xd10 io_uring/poll.c:325
>  io_fallback_req_func+0x126/0x210 io_uring/io_uring.c:246
>  process_one_work+0x93a/0x15a0 kernel/workqueue.c:3261
>  process_scheduled_works kernel/workqueue.c:3344 [inline]
>  worker_thread+0x9b0/0xee0 kernel/workqueue.c:3425
>  kthread+0x711/0x8a0 kernel/kthread.c:463
>  ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
>  </TASK>
>
> Allocated by task 10303:
>  kasan_save_stack mm/kasan/common.c:56 [inline]
>  kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
>  unpoison_slab_object mm/kasan/common.c:339 [inline]
>  __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:365
>  kasan_slab_alloc include/linux/kasan.h:252 [inline]
>  slab_post_alloc_hook mm/slub.c:4948 [inline]
>  slab_alloc_node mm/slub.c:5258 [inline]
>  kmem_cache_alloc_lru_noprof+0x36c/0x6e0 mm/slub.c:5277
>  mqueue_alloc_inode+0x28/0x40 ipc/mqueue.c:502
>  alloc_inode+0x6a/0x1b0 fs/inode.c:346
>  new_inode+0x22/0x170 fs/inode.c:1175
>  mqueue_get_inode+0x27/0xb50 ipc/mqueue.c:297
>  mqueue_create_attr+0x1ac/0x2e0 ipc/mqueue.c:590
>  vfs_mkobj+0xcf/0x290 fs/namei.c:4153
>  prepare_open ipc/mqueue.c:876 [inline]
>  mqueue_file_open ipc/mqueue.c:905 [inline]
>  do_mq_open+0x60d/0x7c0 ipc/mqueue.c:928
>  __do_sys_mq_open ipc/mqueue.c:941 [inline]
>  __se_sys_mq_open ipc/mqueue.c:934 [inline]
>  __x64_sys_mq_open+0x16a/0x1c0 ipc/mqueue.c:934
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Freed by task 0:
>  kasan_save_stack mm/kasan/common.c:56 [inline]
>  kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
>  kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
>  poison_slab_object mm/kasan/common.c:252 [inline]
>  __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
>  kasan_slab_free include/linux/kasan.h:234 [inline]
>  slab_free_hook mm/slub.c:2540 [inline]
>  slab_free mm/slub.c:6663 [inline]
>  kmem_cache_free+0x197/0x620 mm/slub.c:6774
>  rcu_do_batch kernel/rcu/tree.c:2605 [inline]
>  rcu_core+0xd70/0x1870 kernel/rcu/tree.c:2857
>  handle_softirqs+0x27d/0x850 kernel/softirq.c:626
>  __do_softirq kernel/softirq.c:660 [inline]
>  invoke_softirq kernel/softirq.c:496 [inline]
>  __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:727
>  irq_exit_rcu+0x9/0x30 kernel/softirq.c:743
>  instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
>  sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056
>  asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
>
> Last potentially related work creation:
>  kasan_save_stack+0x3e/0x60 mm/kasan/common.c:56
>  kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
>  __call_rcu_common kernel/rcu/tree.c:3119 [inline]
>  call_rcu+0x157/0x9c0 kernel/rcu/tree.c:3239
>  destroy_inode fs/inode.c:401 [inline]
>  evict+0x931/0xae0 fs/inode.c:861
>  __dentry_kill+0x209/0x660 fs/dcache.c:670
>  finish_dput+0xc9/0x480 fs/dcache.c:879
>  __fput+0x68e/0xa70 fs/file_table.c:476
>  task_work_run+0x1d4/0x260 kernel/task_work.c:233
>  resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
>  __exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
>  exit_to_user_mode_loop+0xff/0x4f0 kernel/entry/common.c:75
>  __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
>  syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
>  syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
>  syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
>  do_syscall_64+0x2e3/0xf80 arch/x86/entry/syscall_64.c:100
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> The buggy address belongs to the object at ffff88801c7f2880
>  which belongs to the cache mqueue_inode_cache of size 1576
> The buggy address is located 1232 bytes inside of
>  freed 1576-byte region [ffff88801c7f2880, ffff88801c7f2ea8)
>
> The buggy address belongs to the physical page:
> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88801c7f1440 pfn:0x1c7f0
> head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> memcg:ffff88802ea71f01
> flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
> page_type: f5(slab)
> raw: 00fff00000000040 ffff88801cf88c80 dead000000000122 0000000000000000
> raw: ffff88801c7f1440 000000008012000e 00000000f5000000 ffff88802ea71f01
> head: 00fff00000000040 ffff88801cf88c80 dead000000000122 0000000000000000
> head: ffff88801c7f1440 000000008012000e 00000000f5000000 ffff88802ea71f01
> head: 00fff00000000003 ffffea000071fc01 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 Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 9112271990, free_ts 0
>  set_page_owner include/linux/page_owner.h:32 [inline]
>  post_alloc_hook+0x234/0x290 mm/page_alloc.c:1846
>  prep_new_page mm/page_alloc.c:1854 [inline]
>  get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3915
>  __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
>  alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
>  alloc_slab_page mm/slub.c:3075 [inline]
>  allocate_slab+0x86/0x3b0 mm/slub.c:3248
>  new_slab mm/slub.c:3302 [inline]
>  ___slab_alloc+0xf2b/0x1960 mm/slub.c:4651
>  __slab_alloc+0x65/0x100 mm/slub.c:4774
>  __slab_alloc_node mm/slub.c:4850 [inline]
>  slab_alloc_node mm/slub.c:5246 [inline]
>  kmem_cache_alloc_lru_noprof+0x3fe/0x6e0 mm/slub.c:5277
>  mqueue_alloc_inode+0x28/0x40 ipc/mqueue.c:502
>  alloc_inode+0x6a/0x1b0 fs/inode.c:346
>  new_inode+0x22/0x170 fs/inode.c:1175
>  mqueue_get_inode ipc/mqueue.c:297 [inline]
>  mqueue_fill_super+0xdc/0x380 ipc/mqueue.c:416
>  vfs_get_super fs/super.c:1324 [inline]
>  get_tree_nodev+0xbb/0x150 fs/super.c:1343
>  vfs_get_tree+0x92/0x2a0 fs/super.c:1751
>  fc_mount fs/namespace.c:1209 [inline]
>  fc_mount_longterm+0x1c/0x100 fs/namespace.c:1220
>  mq_create_mount ipc/mqueue.c:486 [inline]
>  mq_init_ns+0x275/0x360 ipc/mqueue.c:1639
> page_owner free stack trace missing
>
> Memory state around the buggy address:
>  ffff88801c7f2c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff88801c7f2c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff88801c7f2d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                                  ^
>  ffff88801c7f2d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff88801c7f2e00: 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 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