WARNING in kmem_cache_free_bulk

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    7cc2a8ea Merge tag 'block-5.8-2020-07-01' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14258fe3100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7be693511b29b338
dashboard link: https://syzkaller.appspot.com/bug?extid=c07ac923fbf6351f6063
compiler:       gcc (GCC) 10.1.0-syz 20200507

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+c07ac923fbf6351f6063@xxxxxxxxxxxxxxxxxxxxxxxxx

------------[ cut here ]------------
virt_to_cache: Object is not a Slab page!
WARNING: CPU: 1 PID: 8538 at mm/slab.h:475 virt_to_cache mm/slab.h:475 [inline]
WARNING: CPU: 1 PID: 8538 at mm/slab.h:475 cache_from_obj mm/slab.h:522 [inline]
WARNING: CPU: 1 PID: 8538 at mm/slab.h:475 cache_from_obj mm/slab.h:506 [inline]
WARNING: CPU: 1 PID: 8538 at mm/slab.h:475 kmem_cache_free_bulk+0x23e/0x290 mm/slab.c:3713
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 8538 Comm: kworker/1:2 Not tainted 5.8.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events kfree_rcu_work
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 panic+0x2e3/0x75c kernel/panic.c:231
 __warn.cold+0x20/0x45 kernel/panic.c:600
 report_bug+0x1bd/0x210 lib/bug.c:198
 handle_bug+0x38/0x90 arch/x86/kernel/traps.c:235
 exc_invalid_op+0x13/0x40 arch/x86/kernel/traps.c:255
 asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:563
RIP: 0010:virt_to_cache mm/slab.h:475 [inline]
RIP: 0010:cache_from_obj mm/slab.h:522 [inline]
RIP: 0010:cache_from_obj mm/slab.h:506 [inline]
RIP: 0010:kmem_cache_free_bulk+0x23e/0x290 mm/slab.c:3713
Code: fe ff ff 80 3d 96 a0 f6 08 00 0f 85 6d fe ff ff 48 c7 c6 e0 f1 55 88 48 c7 c7 08 18 69 89 c6 05 7b a0 f6 08 01 e8 d4 1d 92 ff <0f> 0b e9 4c fe ff ff 48 8b 47 08 48 c7 c6 d0 17 69 89 48 8d 50 ff
RSP: 0018:ffffc90004617c78 EFLAGS: 00010082
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888092772580 RSI: ffffffff815d4f87 RDI: fffff520008c2f81
RBP: ffff888000000000 R08: 0000000000000001 R09: ffff8880ae720fcb
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8880ae7253b0 R14: ffff888000152008 R15: 0000000000000000
 kfree_bulk include/linux/slab.h:412 [inline]
 kfree_rcu_work+0x1a1/0x470 kernel/rcu/tree.c:3069
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293
Kernel Offset: disabled
Rebooting in 86400 seconds..


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