bisecting fixing commit since 775d01b65b5daa002a9ba60f2d2bb3b1a6ce12fb
building syzkaller on 048f2d494ee4a016e2386c28bf8cccdd87896cbd
testing commit 775d01b65b5daa002a9ba60f2d2bb3b1a6ce12fb with gcc (GCC) 8.1.0
kernel signature: 0438e6f01cdd525d9a9c6665070e86951049473f
all runs: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
testing current HEAD c1141b3aab36eb0d9b2bcae4aff69e77d0554386
testing commit c1141b3aab36eb0d9b2bcae4aff69e77d0554386 with gcc (GCC) 8.1.0
kernel signature: 3a34b80dc5c66408d858550cd0fe39584c2358b2
all runs: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
revisions tested: 2, total time: 23m29.115042174s (build: 16m34.336073052s, test: 6m31.221906814s)
the crash still happens on HEAD
commit msg: Linux 4.14.166
crash: KASAN: stack-out-of-bounds Write in ax25_getname
IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready
8021q: adding VLAN 0 to HW filter on device batadv0
==================================================================
BUG: KASAN: stack-out-of-bounds in memset include/linux/string.h:332 [inline]
BUG: KASAN: stack-out-of-bounds in ax25_getname+0x50/0x7e0 net/ax25/af_ax25.c:1409
Write of size 72 at addr ffff88808e6cfcd8 by task syz-executor.5/7957

CPU: 0 PID: 7957 Comm: syz-executor.5 Not tainted 4.14.166-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xf7/0x13b lib/dump_stack.c:58
 print_address_description.cold.7+0x9/0x1c9 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report.cold.8+0x11a/0x2d3 mm/kasan/report.c:409
 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:332 [inline]
 ax25_getname+0x50/0x7e0 net/ax25/af_ax25.c:1409
 get_raw_socket drivers/vhost/net.c:1044 [inline]
 get_socket drivers/vhost/net.c:1101 [inline]
 vhost_net_set_backend drivers/vhost/net.c:1136 [inline]
 vhost_net_ioctl+0xd7b/0x1460 drivers/vhost/net.c:1312
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x74/0x80 fs/ioctl.c:692
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45a219
RSP: 002b:00007f6b9d46bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a219
RDX: 0000000020d7c000 RSI: 000000004008af30 RDI: 0000000000000003
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6b9d46c6d4
R13: 00000000004c56ed R14: 00000000004da738 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea000239b3c0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x1fffc0000000000()
raw: 01fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 0000000100000001 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808e6cfc00: f1 f1 f1 04 f2 f2 f2 f2 f2 f2 f2 04 f2 f2 f2 f2
 ffff88808e6cfc80: f2 f2 f2 00 f2 f2 f2 f2 f2 f2 f2 00 00 00 00 00
>ffff88808e6cfd00: 00 04 f2 f3 f3 f3 f3 00 00 00 00 00 00 00 00 00
                      ^
 ffff88808e6cfd80: 00 00 00 00 f1 f1 f1 f1 00 f2 f2 f2 f2 f2 f2 f2
 ffff88808e6cfe00: 00 00 00 f2 f2 f2 f2 f2 00 00 00 00 f3 f3 f3 f3
==================================================================