bisecting fixing commit since ad326970d25cc85128cd22d62398751ad072efff
building syzkaller on ff4a3345a1b2a40ff1b8b983153d0b1fcc72f1c5
testing commit ad326970d25cc85128cd22d62398751ad072efff with gcc (GCC) 8.4.1 20210217
kernel signature: 7b1341e22e2c6bab5555f1eba9ad5d9573f732d311f573b721ba70e97892a1b6
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in rhashtable_free_and_destroy
testing current HEAD eb575cd5d7f60241d016fdd13a9e86d962093c9b
testing commit eb575cd5d7f60241d016fdd13a9e86d962093c9b with gcc (GCC) 8.4.1 20210217
kernel signature: 0692979b56ce08db75af272bd8ad24677dfadead2fc3ad1f9773ad12a3767cbb
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in rhashtable_free_and_destroy
revisions tested: 2, total time: 24m59.893568431s (build: 17m52.997041145s, test: 6m41.976095573s)
the crash still happens on HEAD
commit msg: Linux 4.19.195
crash: BUG: unable to handle kernel NULL pointer dereference in rhashtable_free_and_destroy
RDX: 0000000000000000 RSI: 00000000200006c0 RDI: 0000000000000003
RBP: 00007f9bce3d21d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007fff84cce59f R14: 00007f9bce3d2300 R15: 0000000000022000
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
PGD 0 P4D 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 14 Comm: kworker/0:1 Not tainted 4.19.195-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events cfg80211_destroy_iface_wk
RIP: 0010:test_and_set_bit arch/x86/include/asm/bitops.h:209 [inline]
RIP: 0010:try_to_grab_pending+0xb8/0x5f0 kernel/workqueue.c:1229
Code: 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 80 3c 02 00 0f 85 0f 04 00 00 4d 89 34 24 e8 41 6a 26 00 45 84 ed 0f 85 54 01 00 00 <f0> 48 0f ba 2b 00 72 11 31 c0 48 83 c4 10 5b 41 5c 41 5d 41 5e 41
RSP: 0018:ffff8881f530f840 EFLAGS: 00010046
RAX: 0000000000000007 RBX: 0000000000000080 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8881f52febcc
RBP: ffff8881f530f878 R08: ffff8881f52fec78 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881f530f8b0
R13: 0000000000000000 R14: 0000000000000282 R15: 0000000000000080
FS:  0000000000000000(0000) GS:ffff8881f6600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 000000000866d002 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __cancel_work_timer+0x9b/0x430 kernel/workqueue.c:2972
 cancel_work_sync+0xb/0x10 kernel/workqueue.c:3049
 rhashtable_free_and_destroy+0x25/0x690 lib/rhashtable.c:1145
 mesh_table_free net/mac80211/mesh_pathtbl.c:73 [inline]
 mesh_pathtbl_unregister+0x43/0xa0 net/mac80211/mesh_pathtbl.c:825
 ieee80211_mesh_teardown_sdata+0x15/0x20 net/mac80211/mesh.c:1478
 ieee80211_teardown_sdata+0x5b/0x70 net/mac80211/iface.c:1122
 ieee80211_uninit+0x10/0x20 net/mac80211/iface.c:1127
 rollback_registered_many+0x828/0xb50 net/core/dev.c:8202
 rollback_registered+0xdc/0x190 net/core/dev.c:8230
 unregister_netdevice_queue+0x186/0x240 net/core/dev.c:9297
 unregister_netdevice include/linux/netdevice.h:2615 [inline]
 ieee80211_if_remove+0x1db/0x2d0 net/mac80211/iface.c:1920
 ieee80211_del_iface+0xd/0x20 net/mac80211/cfg.c:144
 rdev_del_virtual_intf net/wireless/rdev-ops.h:57 [inline]
 cfg80211_destroy_ifaces+0xe3/0x540 net/wireless/core.c:317
 cfg80211_destroy_iface_wk+0x19/0x30 net/wireless/core.c:329
 process_one_work+0x7b9/0x15a0 kernel/workqueue.c:2153
 worker_thread+0x85/0xb60 kernel/workqueue.c:2296
 kthread+0x347/0x410 kernel/kthread.c:259
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Modules linked in:
CR2: 0000000000000080
---[ end trace 7ad5e510ab5d9ea3 ]---
RIP: 0010:test_and_set_bit arch/x86/include/asm/bitops.h:209 [inline]
RIP: 0010:try_to_grab_pending+0xb8/0x5f0 kernel/workqueue.c:1229
Code: 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 80 3c 02 00 0f 85 0f 04 00 00 4d 89 34 24 e8 41 6a 26 00 45 84 ed 0f 85 54 01 00 00 <f0> 48 0f ba 2b 00 72 11 31 c0 48 83 c4 10 5b 41 5c 41 5d 41 5e 41
RSP: 0018:ffff8881f530f840 EFLAGS: 00010046
RAX: 0000000000000007 RBX: 0000000000000080 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8881f52febcc
RBP: ffff8881f530f878 R08: ffff8881f52fec78 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881f530f8b0
R13: 0000000000000000 R14: 0000000000000282 R15: 0000000000000080
FS:  0000000000000000(0000) GS:ffff8881f6600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 000000000866d002 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400