bisecting fixing commit since e42617b825f8073569da76dc4510bfa019b1c35a
building syzkaller on b31eda3df81f62eb7efde0c5d7a9f24ee7e34e6f
testing commit e42617b825f8073569da76dc4510bfa019b1c35a with gcc (GCC) 8.4.1 20210217
kernel signature: 28be4e8a8a2d78c01130333e3480609f088c96653117c109577218fc3df04a66
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: crashed: BUG: unable to handle kernel NULL pointer dereference in llcp_sock_getname
run #10: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #11: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #12: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #13: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #14: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #15: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #16: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #17: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #18: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
run #19: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
testing current HEAD 9f4ad9e425a1d3b6a34617b8ea226d56a119a717
testing commit 9f4ad9e425a1d3b6a34617b8ea226d56a119a717 with gcc (GCC) 10.2.1 20210217
kernel signature: df723844ea5f5fddbf22aa7edecf16d6498c6769d2e679fd3b777b4f3e4f0583
all runs: crashed: KASAN: null-ptr-deref Read in llcp_sock_getname
revisions tested: 2, total time: 19m32.256172315s (build: 11m53.415731958s, test: 6m19.052321573s)
the crash still happens on HEAD
commit msg: Linux 5.12
crash: KASAN: null-ptr-deref Read in llcp_sock_getname
==================================================================
BUG: KASAN: null-ptr-deref in memcpy include/linux/fortify-string.h:191 [inline]
BUG: KASAN: null-ptr-deref in llcp_sock_getname+0x343/0x440 net/nfc/llcp_sock.c:521
Read of size 43 at addr 0000000000000000 by task syz-executor.1/6924

CPU: 1 PID: 6924 Comm: syz-executor.1 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x114/0x14e lib/dump_stack.c:120
 __kasan_report mm/kasan/report.c:403 [inline]
 kasan_report.cold+0x5d/0xd4 mm/kasan/report.c:416
 check_region_inline mm/kasan/generic.c:180 [inline]
 kasan_check_range+0x148/0x190 mm/kasan/generic.c:186
 memcpy+0x24/0x60 mm/kasan/shadow.c:65
 memcpy include/linux/fortify-string.h:191 [inline]
 llcp_sock_getname+0x343/0x440 net/nfc/llcp_sock.c:521
 __sys_getpeername+0x10c/0x200 net/socket.c:1925
 __do_sys_getpeername net/socket.c:1938 [inline]
 __se_sys_getpeername net/socket.c:1935 [inline]
 __x64_sys_getpeername+0x6e/0xb0 net/socket.c:1935
 do_syscall_64+0x32/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
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:00007f187b03b1a8 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: 00007f187b03b6bc
==================================================================