BUG: corrupted list in free_block

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 4d552acf Linux 4.19.34
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16779867200000
kernel config: https://syzkaller.appspot.com/x/.config?x=c95a88291f095edd
dashboard link: https://syzkaller.appspot.com/bug?extid=2441a26d3540d6d725eb
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2441a2...@syzkaller.appspotmail.com

Own node identity fec000000000000000000000000000bb, cluster identity 4711
New replicast peer: 0000:0000:0000:0000:0000:0000:0000:0001
Enabled bearer <udp:syz2>, priority 10
list_del corruption. prev->next should be ffffea00014e2348, but was
ffffea0001db5ec8
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:51!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 14 Comm: kworker/0:1 Not tainted 4.19.34 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: events cache_reap
RIP: 0010:__list_del_entry_valid.cold+0xf/0x4f lib/list_debug.c:51
Code: e8 c9 de 30 fe 0f 0b 48 89 f1 48 c7 c7 a0 a0 81 87 4c 89 e6 e8 b5 de
30 fe 0f 0b 4c 89 f6 48 c7 c7 40 a2 81 87 e8 a4 de 30 fe <0f> 0b 4c 89 ea
4c 89 f6 48 c7 c7 80 a1 81 87 e8 90 de 30 fe 0f 0b
RSP: 0000:ffff8880aa26fbd8 EFLAGS: 00010086
RAX: 0000000000000054 RBX: ffffe8ffffc2fb08 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8155d206 RDI: ffffed101544df6d
RBP: ffff8880aa26fbf0 R08: 0000000000000054 R09: ffffed1015d04fe9
R10: ffffed1015d04fe8 R11: ffff8880ae827f47 R12: ffffea0001dc6988
R13: ffffea0002520b48 R14: ffffea00014e2348 R15: ffffea00014e2348
FS: 0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000000 CR3: 0000000088b0a000 CR4: 00000000001406f0
Call Trace:
__list_del_entry include/linux/list.h:117 [inline]
list_del include/linux/list.h:125 [inline]
free_block+0xd8/0x250 mm/slab.c:3421
drain_array_locked+0x36/0x90 mm/slab.c:2213
drain_array+0x8c/0xb0 mm/slab.c:4027
cache_reap+0xf4/0x280 mm/slab.c:4068
process_one_work+0x98e/0x1760 kernel/workqueue.c:2153
worker_thread+0x98/0xe40 kernel/workqueue.c:2296
kthread+0x357/0x430 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
Modules linked in:

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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.