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

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4:42 PM (7 hours ago) 4:42 PM
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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=578f183e0e144332a0be
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [ax...@kernel.dk io-u...@vger.kernel.org linux-...@vger.kernel.org]

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+578f18...@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
==================================================================


---
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