KASAN: use-after-free Read in rhashtable_last_table

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 958e517f Linux 4.14.230
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1638ba29d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=cdbb0f19434a286f
dashboard link: https://syzkaller.appspot.com/bug?extid=fb4b0db8d4638559f2cb

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fb4b0d...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183 [inline]
BUG: KASAN: use-after-free in rhashtable_last_table+0xfc/0x120 lib/rhashtable.c:252
Read of size 8 at addr ffff88804b1284c0 by task kworker/0:4/9176

CPU: 0 PID: 9176 Comm: kworker/0:4 Not tainted 4.14.230-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events rht_deferred_worker
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x1b2/0x281 lib/dump_stack.c:58
print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
kasan_report_error.cold+0x8a/0x191 mm/kasan/report.c:351
kasan_report mm/kasan/report.c:409 [inline]
__asan_report_load8_noabort+0x68/0x70 mm/kasan/report.c:430
__read_once_size include/linux/compiler.h:183 [inline]
rhashtable_last_table+0xfc/0x120 lib/rhashtable.c:252
rht_deferred_worker+0x8f/0x1890 lib/rhashtable.c:453
process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 9176:
save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
__do_kmalloc_node mm/slab.c:3682 [inline]
__kmalloc_node+0x4c/0x70 mm/slab.c:3689
kmalloc_node include/linux/slab.h:530 [inline]
kvmalloc_node+0x88/0xd0 mm/util.c:397
kvmalloc include/linux/mm.h:531 [inline]
kvzalloc include/linux/mm.h:539 [inline]
bucket_table_alloc+0x3a5/0x5d0 lib/rhashtable.c:217
rhashtable_rehash_alloc+0x63/0x1f0 lib/rhashtable.c:396
rhashtable_shrink lib/rhashtable.c:440 [inline]
rht_deferred_worker+0x3fb/0x1890 lib/rhashtable.c:458
process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Freed by task 9274:
save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kfree+0xc9/0x250 mm/slab.c:3815
kvfree+0x45/0x50 mm/util.c:416
rhashtable_free_and_destroy+0x20a/0x710 lib/rhashtable.c:1093
ops_exit_list+0xa5/0x150 net/core/net_namespace.c:142
cleanup_net+0x3b3/0x840 net/core/net_namespace.c:484
process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

The buggy address belongs to the object at ffff88804b128480
which belongs to the cache kmalloc-8192 of size 8192
The buggy address is located 64 bytes inside of
8192-byte region [ffff88804b128480, ffff88804b12a480)
The buggy address belongs to the page:
page:ffffea00012c4a00 count:1 mapcount:0 mapping:ffff88804b128480 index:0x0 compound_mapcount: 0
flags: 0xfff00000008100(slab|head)
raw: 00fff00000008100 ffff88804b128480 0000000000000000 0000000100000001
raw: ffffea00010b8120 ffffea000113cd20 ffff88813fe09080 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88804b128380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88804b128400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88804b128480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88804b128500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88804b128580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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[syzbot]

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