Message-ID: <687bd5fe.a70a0220.693ce.0091.GAE@google.com>
Date: Sat, 19 Jul 2025 10:29:34 -0700
From: syzbot <syzbot+01523a0ae5600aef5895@...kaller.appspotmail.com>
To: axboe@...nel.dk, io-uring@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [io-uring?] KASAN: slab-use-after-free Read in io_poll_remove_entries

Hello,

syzbot found the following issue on:

HEAD commit:    4871b7cb27f4 Merge tag 'v6.16-rc6-smb3-client-fixes' of gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1288c38c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa738a4418f051ee
dashboard link: https://syzkaller.appspot.com/bug?extid=01523a0ae5600aef5895
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=1688c38c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=166ed7d4580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-4871b7cb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4a9dea51d821/vmlinux-4871b7cb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f96c723cdfe6/bzImage-4871b7cb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+01523a0ae5600aef5895@...kaller.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+0x36/0x50 kernel/locking/spinlock.c:170
Read of size 1 at addr ffff88803c6f42b0 by task kworker/2:2/1339

CPU: 2 UID: 0 PID: 1339 Comm: kworker/2:2 Not tainted 6.16.0-rc6-syzkaller-00253-g4871b7cb27f4 #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: events io_fallback_req_func
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/0x610 mm/kasan/report.c:480
 kasan_report+0xe0/0x110 mm/kasan/report.c:593
 __kasan_check_byte+0x36/0x50 mm/kasan/common.c:557
 kasan_check_byte include/linux/kasan.h:399 [inline]
 lock_acquire kernel/locking/lockdep.c:5845 [inline]
 lock_acquire+0xfc/0x350 kernel/locking/lockdep.c:5828
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0x36/0x50 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.part.0+0x14e/0x7e0 io_uring/poll.c:179
 io_poll_remove_entries io_uring/poll.c:159 [inline]
 io_poll_task_func+0x4cd/0x1130 io_uring/poll.c:326
 io_fallback_req_func+0x1c7/0x6d0 io_uring/io_uring.c:259
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
 kthread+0x3c5/0x780 kernel/kthread.c:464
 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6154:
 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]
 __comedi_device_postconfig_async drivers/comedi/drivers.c:664 [inline]
 __comedi_device_postconfig drivers/comedi/drivers.c:721 [inline]
 comedi_device_postconfig+0x2cb/0xc80 drivers/comedi/drivers.c:756
 comedi_device_attach+0x3cf/0x900 drivers/comedi/drivers.c:998
 do_devconfig_ioctl+0x1a7/0x580 drivers/comedi/comedi_fops.c:855
 comedi_unlocked_ioctl+0x15bb/0x2e90 drivers/comedi/comedi_fops.c:2136
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl fs/ioctl.c:893 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
 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 6156:
 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
 comedi_device_detach_cleanup drivers/comedi/drivers.c:171 [inline]
 comedi_device_detach+0x2a4/0x9e0 drivers/comedi/drivers.c:208
 do_devconfig_ioctl+0x46c/0x580 drivers/comedi/comedi_fops.c:833
 comedi_unlocked_ioctl+0x15bb/0x2e90 drivers/comedi/comedi_fops.c:2136
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl fs/ioctl.c:893 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
 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

The buggy address belongs to the object at ffff88803c6f4200
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 176 bytes inside of
 freed 256-byte region [ffff88803c6f4200, ffff88803c6f4300)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3c6f4
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 ffff88801b842b40 ffffea0000f0c180 dead000000000004
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b842b40 ffffea0000f0c180 dead000000000004
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffea0000f1bd01 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 6018, tgid 6018 (syz-executor), ts 49909540314, free_ts 49907641430
 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]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_node_track_caller_noprof+0x2ee/0x510 mm/slub.c:4347
 kmemdup_noprof+0x29/0x60 mm/util.c:137
 ipt_register_table+0x224/0x430 net/ipv4/netfilter/ip_tables.c:1770
 iptable_filter_table_init+0x75/0xa0 net/ipv4/netfilter/iptable_filter.c:49
 xt_find_table_lock+0x2e4/0x520 net/netfilter/x_tables.c:1260
 xt_request_find_table_lock+0x28/0xf0 net/netfilter/x_tables.c:1285
 get_info+0x19c/0x7c0 net/ipv4/netfilter/ip_tables.c:963
 do_ipt_get_ctl+0x169/0xaa0 net/ipv4/netfilter/ip_tables.c:1659
 nf_getsockopt+0x7c/0xe0 net/netfilter/nf_sockopt.c:116
page last free pid 6018 tgid 6018 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
 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:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4148 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 kmem_cache_alloc_noprof+0x1cb/0x3b0 mm/slub.c:4204
 getname_flags.part.0+0x4c/0x550 fs/namei.c:146
 getname_flags+0x93/0xf0 include/linux/audit.h:322
 getname include/linux/fs.h:2907 [inline]
 __do_sys_mkdirat fs/namei.c:4425 [inline]
 __se_sys_mkdirat fs/namei.c:4423 [inline]
 __x64_sys_mkdirat+0x76/0xb0 fs/namei.c:4423
 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

Memory state around the buggy address:
 ffff88803c6f4180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88803c6f4200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88803c6f4280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff88803c6f4300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88803c6f4380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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