bisecting fixing commit since c555efaf14026c7751fa68d87403a5eb5ae7dcaf
building syzkaller on 048f2d494ee4a016e2386c28bf8cccdd87896cbd
testing commit c555efaf14026c7751fa68d87403a5eb5ae7dcaf with gcc (GCC) 8.1.0
kernel signature: ba5cd0985583ffcd134e5b2e8cb358934790421f
all runs: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
testing current HEAD 7d120bf21c05cbe30a679f0feeca884eeaceb069
testing commit 7d120bf21c05cbe30a679f0feeca884eeaceb069 with gcc (GCC) 8.1.0
kernel signature: 6b9e5029edb291533844e86834ab1d12cabd9fc1
all runs: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
revisions tested: 2, total time: 23m32.754832014s (build: 16m42.662317336s, test: 6m16.968698298s)
the crash still happens on HEAD
commit msg: Linux 4.19.90
crash: KASAN: stack-out-of-bounds Write in ax25_getname
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
8021q: adding VLAN 0 to HW filter on device batadv0
==================================================================
BUG: KASAN: stack-out-of-bounds in memset include/linux/string.h:333 [inline]
BUG: KASAN: stack-out-of-bounds in ax25_getname+0x4d/0x7b0 net/ax25/af_ax25.c:1408
Write of size 72 at addr ffff88808d20fc78 by task syz-executor.1/7099

CPU: 0 PID: 7099 Comm: syz-executor.1 Not tainted 4.19.90-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+0x123/0x177 lib/dump_stack.c:118
 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
 memset+0x23/0x40 mm/kasan/kasan.c:285
 memset include/linux/string.h:333 [inline]
 ax25_getname+0x4d/0x7b0 net/ax25/af_ax25.c:1408
 get_raw_socket drivers/vhost/net.c:1206 [inline]
 get_socket drivers/vhost/net.c:1262 [inline]
 vhost_net_set_backend drivers/vhost/net.c:1297 [inline]
 vhost_net_ioctl+0xe41/0x1500 drivers/vhost/net.c:1488
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688
 ksys_ioctl+0x62/0x90 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 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:00007f931b31bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a219
RDX: 0000000020d7c000 RSI: 000000004008af30 RDI: 0000000000000003
RBP: 000000000075c118 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f931b31c6d4
R13: 00000000004c56ed R14: 00000000004da738 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea00023483c0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x1fffc0000000000()
raw: 01fffc0000000000 0000000000000000 ffffffff02340101 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808d20fb80: 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 04
 ffff88808d20fc00: f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 f2 f2 f2 f2 00
>ffff88808d20fc80: 00 00 00 00 00 04 f2 00 00 00 00 00 00 00 00 00
                                  ^
 ffff88808d20fd00: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 f2 f2 f2
 ffff88808d20fd80: f2 f2 f2 f2 00 00 00 f2 f2 f2 f2 f2 00 00 00 00
==================================================================