KASAN: use-after-free Read in rhashtable_last_table

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dfb57161 Linux 4.19.178
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16119cfad00000
kernel config: https://syzkaller.appspot.com/x/.config?x=c227024aa159411f
dashboard link: https://syzkaller.appspot.com/bug?extid=ec140277e7d1f6188dd4

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+ec1402...@syzkaller.appspotmail.com

IPv6: ADDRCONF(NETDEV_UP): veth0_virt_wifi: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth1_virt_wifi: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_virt_wifi: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_virt_wifi: link becomes ready
==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:207 [inline]
BUG: KASAN: use-after-free in rhashtable_last_table+0x167/0x180 lib/rhashtable.c:217
Read of size 8 at addr ffff88804fd51780 by task kworker/1:2/22829

CPU: 1 PID: 22829 Comm: kworker/1:2 Not tainted 4.19.178-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:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
kasan_report_error.cold+0x8a/0x1b9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
__read_once_size include/linux/compiler.h:207 [inline]
rhashtable_last_table+0x167/0x180 lib/rhashtable.c:217
rht_deferred_worker+0xa7/0x1b20 lib/rhashtable.c:410
process_one_work+0x864/0x1570 kernel/workqueue.c:2152
worker_thread+0x64c/0x1130 kernel/workqueue.c:2295
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 22829:
__do_kmalloc_node mm/slab.c:3689 [inline]
__kmalloc_node+0x4c/0x70 mm/slab.c:3696
kmalloc_node include/linux/slab.h:557 [inline]
kvmalloc_node+0xb4/0xf0 mm/util.c:423
kvmalloc include/linux/mm.h:577 [inline]
kvzalloc include/linux/mm.h:585 [inline]
bucket_table_alloc+0x3a/0x440 lib/rhashtable.c:176
rhashtable_rehash_alloc+0x6b/0x120 lib/rhashtable.c:353
rht_deferred_worker+0x18a/0x1b20 lib/rhashtable.c:413
process_one_work+0x864/0x1570 kernel/workqueue.c:2152
worker_thread+0x64c/0x1130 kernel/workqueue.c:2295
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Freed by task 147:
__cache_free mm/slab.c:3503 [inline]
kfree+0xcc/0x210 mm/slab.c:3822
kvfree+0x59/0x60 mm/util.c:452
rhashtable_free_and_destroy+0x15e/0x970 lib/rhashtable.c:1167
ops_exit_list+0xa5/0x150 net/core/net_namespace.c:153
cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:553
process_one_work+0x864/0x1570 kernel/workqueue.c:2152
worker_thread+0x64c/0x1130 kernel/workqueue.c:2295
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

The buggy address belongs to the object at ffff88804fd51740
which belongs to the cache kmalloc-8192 of size 8192
The buggy address is located 64 bytes inside of
8192-byte region [ffff88804fd51740, ffff88804fd53740)
The buggy address belongs to the page:
page:ffffea00013f5400 count:1 mapcount:0 mapping:ffff88813bff2080 index:0x0 compound_mapcount: 0
flags: 0xfff00000008100(slab|head)
raw: 00fff00000008100 ffffea0002a37208 ffffea0002c1ef08 ffff88813bff2080
raw: 0000000000000000 ffff88804fd51740 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88804fd51680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88804fd51700: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff88804fd51780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88804fd51800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88804fd51880: 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.