bisecting fixing commit since 4dd58158254c8a027f2bf5060b72ef64cafa3b9d
building syzkaller on d797d2018f9550530c469ce03b5ae36cfa1ebd23
testing commit 4dd58158254c8a027f2bf5060b72ef64cafa3b9d with gcc (GCC) 8.1.0
kernel signature: 4be742c12581b5335328fa1b630ec8fbeab58a1eea72e400e24e91ffc0e96f33
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: BUG: unable to handle kernel NULL pointer dereference 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: BUG: unable to handle kernel NULL pointer dereference 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: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
testing current HEAD fb33c6510d5595144d585aa194d377cf74d31911
testing commit fb33c6510d5595144d585aa194d377cf74d31911 with gcc (GCC) 8.1.0
kernel signature: 1618c56ca423051fc65ed497db3b87e443fe2b0ce6e6e3de4202db2b09efdc2b
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: BUG: unable to handle kernel NULL pointer dereference in llcp_sock_getname
run #7: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #8: crashed: BUG: unable to handle kernel NULL pointer dereference in llcp_sock_getname
run #9: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
revisions tested: 2, total time: 19m54.812929344s (build: 11m59.082653462s, test: 7m5.986227661s)
the crash still happens on HEAD
commit msg: Linux 5.6-rc6
crash: KASAN: null-ptr-deref Read in llcp_sock_getname
==================================================================
BUG: KASAN: null-ptr-deref in memcpy include/linux/string.h:381 [inline]
BUG: KASAN: null-ptr-deref in llcp_sock_getname+0x341/0x440 net/nfc/llcp_sock.c:519
Read of size 1 at addr 0000000000000000 by task syz-executor.3/8435

CPU: 0 PID: 8435 Comm: syz-executor.3 Not tainted 5.6.0-rc6-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+0x12d/0x187 lib/dump_stack.c:118
 __kasan_report.cold.11+0x5/0x32 mm/kasan/report.c:510
 kasan_report+0x12/0x20 mm/kasan/common.c:641
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x153/0x1d0 mm/kasan/generic.c:192
 memcpy+0x23/0x50 mm/kasan/common.c:127
 memcpy include/linux/string.h:381 [inline]
 llcp_sock_getname+0x341/0x440 net/nfc/llcp_sock.c:519
 __sys_getpeername+0x123/0x220 net/socket.c:1946
 __do_sys_getpeername net/socket.c:1959 [inline]
 __se_sys_getpeername net/socket.c:1956 [inline]
 __x64_sys_getpeername+0x6e/0xb0 net/socket.c:1956
 do_syscall_64+0xca/0x630 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a219
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f958ee76c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000034
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a219
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f958ee776d4
R13: 00000000004c0f29 R14: 00000000004d3dd8 R15: 00000000ffffffff
==================================================================