bisecting fixing commit since 5b7a52cd2eef952cee8a72512ef370bcdef46636
building syzkaller on be6b1582e9ce6f1ac5d8978e70a6a9f91113f238
testing commit 5b7a52cd2eef952cee8a72512ef370bcdef46636 with gcc (GCC) 8.4.1 20210217
kernel signature: e02d620757a1c62104ca523825ff55393203a78ad3fdfb86f4ee848b60acc009
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in rhashtable_free_and_destroy
testing current HEAD 29c52025152bab4c557d8174da58f1a4c8e70438
testing commit 29c52025152bab4c557d8174da58f1a4c8e70438 with gcc (GCC) 8.4.1 20210217
kernel signature: ee6154359061138739ae6378a4820fb6029ccc978a8870d28c29f61e46c7c88e
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in rhashtable_free_and_destroy
revisions tested: 2, total time: 21m40.42863038s (build: 14m10.563238459s, test: 6m34.587744506s)
the crash still happens on HEAD
commit msg: Linux 4.14.221
crash: BUG: unable to handle kernel NULL pointer dereference in rhashtable_free_and_destroy
RDX: 0000000000000000 RSI: 00000000200006c0 RDI: 0000000000000003
RBP: 00007f8ee8c301d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffd8861884f R14: 00007f8ee8c30300 R15: 0000000000022000
BUG: unable to handle kernel NULL pointer dereference at 0000000000000088
IP: test_and_set_bit arch/x86/include/asm/bitops.h:220 [inline]
IP: try_to_grab_pending+0xb8/0x5a0 kernel/workqueue.c:1230
PGD 0 P4D 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 8879 Comm: kworker/0:4 Not tainted 4.14.221-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events cfg80211_destroy_iface_wk
task: ffff8881f3bec440 task.stack: ffff8881f4628000
RIP: 0010:test_and_set_bit arch/x86/include/asm/bitops.h:220 [inline]
RIP: 0010:try_to_grab_pending+0xb8/0x5a0 kernel/workqueue.c:1230
RSP: 0018:ffff8881f462f858 EFLAGS: 00010046
RAX: 0000000000000007 RBX: 0000000000000088 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8881f3becc8c
RBP: ffff8881f462f890 R08: ffff8881f3becd38 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881f462f8c8
R13: 0000000000000000 R14: 0000000000000286 R15: 0000000000000088
FS:  0000000000000000(0000) GS:ffff8881f6400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000088 CR3: 0000000008e6a002 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __cancel_work_timer+0x93/0x420 kernel/workqueue.c:2923
 cancel_work_sync+0xb/0x10 kernel/workqueue.c:3000
 rhashtable_free_and_destroy+0x25/0x5e0 lib/rhashtable.c:1073
 mesh_table_free net/mac80211/mesh_pathtbl.c:71 [inline]
 mesh_pathtbl_unregister+0x43/0xa0 net/mac80211/mesh_pathtbl.c:904
 ieee80211_mesh_teardown_sdata+0x15/0x20 net/mac80211/mesh.c:1479
 ieee80211_teardown_sdata+0x1c4/0x270 net/mac80211/iface.c:1142
 ieee80211_uninit+0x10/0x20 net/mac80211/iface.c:1147
 rollback_registered_many+0x769/0xb70 net/core/dev.c:7217
 rollback_registered+0xd4/0x180 net/core/dev.c:7245
 unregister_netdevice_queue net/core/dev.c:8266 [inline]
 unregister_netdevice_queue+0x17e/0x200 net/core/dev.c:8259
 unregister_netdevice include/linux/netdevice.h:2442 [inline]
 ieee80211_if_remove+0x1d7/0x290 net/mac80211/iface.c:1939
 ieee80211_del_iface+0xd/0x20 net/mac80211/cfg.c:143
 rdev_del_virtual_intf net/wireless/rdev-ops.h:57 [inline]
 cfg80211_destroy_ifaces+0xe3/0x5c0 net/wireless/core.c:317
 cfg80211_destroy_iface_wk+0x19/0x30 net/wireless/core.c:329
 process_one_work+0x74f/0x1620 kernel/workqueue.c:2116
 worker_thread+0xcc/0xee0 kernel/workqueue.c:2250
 kthread+0x338/0x400 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Code: 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 80 3c 02 00 0f 85 cc 03 00 00 4d 89 34 24 e8 31 d7 0a 00 45 84 ed 0f 85 3a 01 00 00 <f0> 48 0f ba 2b 00 72 11 31 c0 48 83 c4 10 5b 41 5c 41 5d 41 5e 
RIP: test_and_set_bit arch/x86/include/asm/bitops.h:220 [inline] RSP: ffff8881f462f858
RIP: try_to_grab_pending+0xb8/0x5a0 kernel/workqueue.c:1230 RSP: ffff8881f462f858
CR2: 0000000000000088
---[ end trace b427c2e3ad73bd68 ]---