[v6.1] KASAN: use-after-free Read in md_start_sync

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1a8763b93150 Linux 6.1.188
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=166faa05580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e5b41322189806a
dashboard link: https://syzkaller.appspot.com/bug?extid=6bdb70d0923b8a3092ce
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/79d582e9ec4f/disk-1a8763b9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/70e43b512b19/vmlinux-1a8763b9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7107d5b60093/Image-1a8763b9.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6bdb70...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x104/0x6634 kernel/locking/lockdep.c:4933
Read of size 8 at addr ffff0000ce5fd928 by task kworker/0:1/12804

CPU: 0 PID: 12804 Comm: kworker/0:1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026
Workqueue: md_misc md_start_sync
Call trace:
dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
__dump_stack+0x30/0x40 lib/dump_stack.c:88
dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
print_address_description+0x88/0x218 mm/kasan/report.c:316
print_report+0x50/0x68 mm/kasan/report.c:420
kasan_report+0xa8/0xfc mm/kasan/report.c:524
__asan_report_load8_noabort+0x2c/0x38 mm/kasan/report_generic.c:351
__lock_acquire+0x104/0x6634 kernel/locking/lockdep.c:4933
lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5678
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x6c/0xb0 kernel/locking/spinlock.c:162
__wake_up_common_lock kernel/sched/wait.c:137 [inline]
__wake_up+0xe8/0x180 kernel/sched/wait.c:160
md_wakeup_thread drivers/md/md.c:8018 [inline]
md_start_sync+0x9c/0x3b4 drivers/md/md.c:9356
process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292
worker_thread+0x8cc/0xfe8 kernel/workqueue.c:2439
kthread+0x254/0x2e0 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Allocated by task 12804:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:505
____kasan_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:384
kasan_kmalloc include/linux/kasan.h:211 [inline]
kmalloc_trace+0x7c/0x94 mm/slab_common.c:1031
kmalloc include/linux/slab.h:563 [inline]
kzalloc include/linux/slab.h:699 [inline]
md_register_thread+0x64/0x1ac drivers/md/md.c:8028
md_start_sync+0x3c/0x3b4 drivers/md/md.c:9338
process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292
worker_thread+0x8cc/0xfe8 kernel/workqueue.c:2439
kthread+0x254/0x2e0 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Freed by task 14208:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
kasan_save_free_info+0x38/0x5c mm/kasan/generic.c:516
____kasan_slab_free+0x148/0x1b0 mm/kasan/common.c:237
__kasan_slab_free+0x18/0x28 mm/kasan/common.c:245
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1729 [inline]
slab_free_freelist_hook+0x16c/0x1e8 mm/slub.c:1755
slab_free mm/slub.c:3687 [inline]
__kmem_cache_free+0xbc/0x21c mm/slub.c:3700
kfree+0xd0/0x1a8 mm/slab_common.c:988
md_unregister_thread+0x9c/0x12c drivers/md/md.c:8068
md_check_recovery+0x8bc/0x1334 drivers/md/md.c:9490
raid5d+0x108/0x1394 drivers/md/raid5.c:6802
md_thread+0x1e0/0x3cc drivers/md/md.c:8007
kthread+0x254/0x2e0 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Last potentially related work creation:
kasan_save_stack+0x40/0x70 mm/kasan/common.c:46
__kasan_record_aux_stack+0xc0/0xdc mm/kasan/generic.c:486
kasan_record_aux_stack_noalloc+0x14/0x20 mm/kasan/generic.c:496
kvfree_call_rcu+0xb4/0x6f0 kernel/rcu/tree.c:3405
cfg80211_update_known_bss+0x11c/0x7fc net/wireless/scan.c:-1
cfg80211_bss_update+0x150/0x1ccc net/wireless/scan.c:1847
cfg80211_inform_single_bss_frame_data net/wireless/scan.c:2509 [inline]
cfg80211_inform_bss_frame_data+0x890/0x10f8 net/wireless/scan.c:2542
ieee80211_bss_info_update+0x640/0xa7c net/mac80211/scan.c:190
ieee80211_rx_bss_info net/mac80211/ibss.c:1120 [inline]
ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1609 [inline]
ieee80211_ibss_rx_queued_mgmt+0x143c/0x2608 net/mac80211/ibss.c:1638
ieee80211_iface_process_skb net/mac80211/iface.c:1685 [inline]
ieee80211_iface_work+0x5a8/0xa4c net/mac80211/iface.c:1739
cfg80211_wiphy_work+0x1e0/0x220 net/wireless/core.c:433
process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292
worker_thread+0x8cc/0xfe8 kernel/workqueue.c:2439
kthread+0x254/0x2e0 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Second to last potentially related work creation:
kasan_save_stack+0x40/0x70 mm/kasan/common.c:46
__kasan_record_aux_stack+0xc0/0xdc mm/kasan/generic.c:486
kasan_record_aux_stack_noalloc+0x14/0x20 mm/kasan/generic.c:496
kvfree_call_rcu+0xb4/0x6f0 kernel/rcu/tree.c:3405
cfg80211_update_known_bss+0x11c/0x7fc net/wireless/scan.c:-1
cfg80211_bss_update+0x150/0x1ccc net/wireless/scan.c:1847
cfg80211_inform_single_bss_frame_data net/wireless/scan.c:2509 [inline]
cfg80211_inform_bss_frame_data+0x890/0x10f8 net/wireless/scan.c:2542
ieee80211_bss_info_update+0x640/0xa7c net/mac80211/scan.c:190
ieee80211_rx_bss_info net/mac80211/ibss.c:1120 [inline]
ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1609 [inline]
ieee80211_ibss_rx_queued_mgmt+0x143c/0x2608 net/mac80211/ibss.c:1638
ieee80211_iface_process_skb net/mac80211/iface.c:1685 [inline]
ieee80211_iface_work+0x5a8/0xa4c net/mac80211/iface.c:1739
cfg80211_wiphy_work+0x1e0/0x220 net/wireless/core.c:433
process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292
worker_thread+0x8cc/0xfe8 kernel/workqueue.c:2439
kthread+0x254/0x2e0 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

The buggy address belongs to the object at ffff0000ce5fd900
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 40 bytes inside of
128-byte region [ffff0000ce5fd900, ffff0000ce5fd980)

The buggy address belongs to the physical page:
page:00000000050d0685 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10e5fd
flags: 0x5ffc00000000200(slab|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000200 0000000000000000 dead000000000001 ffff0000c0002300
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff0000ce5fd800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff0000ce5fd880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff0000ce5fd900: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff0000ce5fd980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff0000ce5fda00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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