bisecting fixing commit since fb683b5e3f53a73e761952735736180939a313df
building syzkaller on 1508f45368a309a3b1196a342b3d64ce7be4cc43
testing commit fb683b5e3f53a73e761952735736180939a313df with gcc (GCC) 8.4.1 20210217
kernel signature: 2234a03aee21f140abd837632762f85111a65bc466e26456af3c1afbd320d2d7
all runs: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
testing current HEAD dfb571610ba392179348c8472bfb131d4173d585
testing commit dfb571610ba392179348c8472bfb131d4173d585 with gcc (GCC) 8.4.1 20210217
kernel signature: e5a72d7d3e680ede182b6f832535276a34168a060def11f095b99e3856b578da
run #0: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #1: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #2: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #3: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #4: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #5: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #6: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #7: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #8: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #9: boot failed: can't ssh into the instance
revisions tested: 2, total time: 31m14.082820341s (build: 16m12.251071285s, test: 13m42.925669928s)
the crash still happens on HEAD
commit msg: Linux 4.19.178
crash: KASAN: null-ptr-deref Read in llcp_sock_getname
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready
8021q: adding VLAN 0 to HW filter on device batadv0
8021q: adding VLAN 0 to HW filter on device batadv0
8021q: adding VLAN 0 to HW filter on device batadv0
==================================================================
BUG: KASAN: null-ptr-deref in memcpy include/linux/string.h:377 [inline]
BUG: KASAN: null-ptr-deref in llcp_sock_getname+0x341/0x440 net/nfc/llcp_sock.c:531
Read of size 43 at addr 0000000000000000 by task syz-executor.3/6778

CPU: 0 PID: 6778 Comm: syz-executor.3 Not tainted 4.19.178-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+0x123/0x171 lib/dump_stack.c:118
 kasan_report_error mm/kasan/report.c:352 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold.9+0x6d/0x2fe mm/kasan/report.c:396
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
 memcpy+0x23/0x50 mm/kasan/kasan.c:302
 memcpy include/linux/string.h:377 [inline]
 llcp_sock_getname+0x341/0x440 net/nfc/llcp_sock.c:531
 __sys_getpeername+0x123/0x220 net/socket.c:1735
 __do_sys_getpeername net/socket.c:1748 [inline]
 __se_sys_getpeername net/socket.c:1745 [inline]
 __x64_sys_getpeername+0x6e/0xb0 net/socket.c:1745
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x462079
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:00007f85d5a1b1a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000034
RAX: ffffffffffffffda RBX: 000000000052bf00 RCX: 0000000000462079
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004ee838 R14: 00000000004ad1ad R15: 00007f85d5a1b6bc
==================================================================