bisecting fixing commit since 0c88e405c97ed1828443b67891e6d4bb6e56cd4e
building syzkaller on a0092f9dfdd33924abe5cf5565e4ec4748217c7b
testing commit 0c88e405c97ed1828443b67891e6d4bb6e56cd4e with gcc (GCC) 8.4.1 20210217
kernel signature: 955bec0dfe34247ab3e08ea68d64524dfcf49710771c0991b843971995e988a1
run #0: crashed: WARNING in inc_nlink
run #1: crashed: WARNING in inc_nlink
run #2: crashed: WARNING in inc_nlink
run #3: crashed: WARNING in inc_nlink
run #4: crashed: WARNING in inc_nlink
run #5: crashed: WARNING in inc_nlink
run #6: crashed: WARNING in inc_nlink
run #7: crashed: WARNING in inc_nlink
run #8: crashed: WARNING in inc_nlink
run #9: crashed: WARNING in corrupted
run #10: crashed: WARNING in inc_nlink
run #11: crashed: WARNING in inc_nlink
run #12: crashed: WARNING in inc_nlink
run #13: crashed: WARNING in inc_nlink
run #14: crashed: WARNING in inc_nlink
run #15: crashed: WARNING in inc_nlink
run #16: crashed: WARNING in inc_nlink
run #17: crashed: WARNING in inc_nlink
run #18: crashed: WARNING in inc_nlink
run #19: crashed: WARNING in inc_nlink
testing current HEAD 9f84340f012ee60c12aacc03662bcdd67419a31a
testing commit 9f84340f012ee60c12aacc03662bcdd67419a31a with gcc (GCC) 8.4.1 20210217
kernel signature: 118cb102f6481e7b9ccbadb83f6f8e5179cc317b18cd3bf3a60079eb7a74722d
run #0: crashed: WARNING in inc_nlink
run #1: crashed: WARNING in inc_nlink
run #2: crashed: WARNING in inc_nlink
run #3: crashed: WARNING in corrupted
run #4: crashed: WARNING in inc_nlink
run #5: crashed: WARNING in inc_nlink
run #6: crashed: WARNING in inc_nlink
run #7: crashed: WARNING in inc_nlink
run #8: crashed: WARNING in inc_nlink
run #9: crashed: WARNING in inc_nlink
revisions tested: 2, total time: 23m1.676651681s (build: 16m2.917248345s, test: 6m28.932182023s)
the crash still happens on HEAD
commit msg: Linux 4.19.196
crash: WARNING in inc_nlink
wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
------------[ cut here ]------------
IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
WARNING: CPU: 1 PID: 9875 at fs/inode.c:343 inc_nlink.cold.15+0xc/0x13 fs/inode.c:343
Kernel panic - not syncing: panic_on_warn set ...

wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
CPU: 1 PID: 9875 Comm: syz-executor.2 Not tainted 4.19.196-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x17c/0x226 lib/dump_stack.c:118
ieee80211 phy11: Selected rate control algorithm 'minstrel_ht'
 panic+0x1cd/0x375 kernel/panic.c:186
 __warn.cold.7+0x1b/0x36 kernel/panic.c:541
 report_bug+0x1a1/0x200 lib/bug.c:183
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 fixup_bug arch/x86/kernel/traps.c:173 [inline]
 do_error_trap+0x200/0x350 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1038
RIP: 0010:inc_nlink.cold.15+0xc/0x13 fs/inode.c:343
Code: e4 03 ff ff 0f 0b e9 79 75 17 fa 48 c7 c7 e0 88 13 88 e8 d1 03 ff ff 0f 0b e9 b6 75 17 fa 48 c7 c7 00 91 13 88 e8 be 03 ff ff <0f> 0b e9 3c 8f 17 fa 48 8d 7b 40 b8 ff ff 37 00 48 89 fa 48 c1 e0
RSP: 0018:ffff88808dbdfd98 EFLAGS: 00010282
RAX: 0000000000000024 RBX: ffff888080da6988 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff88502040 RDI: ffffffff8bad8720
RBP: ffff88808dbdfdb8 R08: ffffed1017464e99 R09: ffffed1017464e98
R10: ffffed1017464e98 R11: ffff8880ba3274c7 R12: ffff888080da69d0
R13: ffff88808dd929e0 R14: 00000000000000a8 R15: ffff88808dd92a38
 inode_inc_link_count include/linux/fs.h:2101 [inline]
 sysv_mkdir+0x18/0x100 fs/sysv/namei.c:131
 vfs_mkdir+0x37f/0x620 fs/namei.c:3819
 do_mkdirat+0x1c2/0x220 fs/namei.c:3842
 __do_sys_mkdirat fs/namei.c:3853 [inline]
 __se_sys_mkdirat fs/namei.c:3851 [inline]
 __x64_sys_mkdirat+0x71/0xb0 fs/namei.c:3851
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x465889
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb875ac7188 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 000000000055bf00 RCX: 0000000000465889
RDX: 00000000000000b8 RSI: 0000000020000040 RDI: 0000000000000005
RBP: 00000000004af68d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf00
R13: 00007ffdbb68ef8f R14: 00007fb875ac7300 R15: 0000000000022000
Kernel Offset: disabled
Rebooting in 86400 seconds..