bisecting fixing commit since 6c9594bdd47412ebf74616593b9dcad67c4e9e00
building syzkaller on d5696d51924aeb6957c19b616c888f58fe9a3740
testing commit 6c9594bdd47412ebf74616593b9dcad67c4e9e00 with gcc (GCC) 8.1.0
kernel signature: 2b15c1561404d4ac2269def8347aa93f95c520bda0d48565ae72437198677aae
all runs: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
testing current HEAD 0bf999f9c5e74c7ecf9dafb527146601e5c848b9
testing commit 0bf999f9c5e74c7ecf9dafb527146601e5c848b9 with gcc (GCC) 8.1.0
kernel signature: ccccead673bbdf1dfbf3c41ff53a3b2ed76ecc3816968d9869ccb7211181d78c
run #0: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
run #1: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
run #2: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
run #3: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
run #4: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
run #5: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
run #6: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
run #7: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
run #8: crashed: KASAN: stack-out-of-bounds Write in ax25_getname
run #9: boot failed: can't ssh into the instance
revisions tested: 2, total time: 28m17.801818142s (build: 12m36.765982139s, test: 14m59.901207149s)
the crash still happens on HEAD
commit msg: linux/pipe_fs_i.h: fix kernel-doc warnings after @wait was split
crash: KASAN: stack-out-of-bounds Write in ax25_getname
==================================================================
BUG: KASAN: stack-out-of-bounds in memset include/linux/string.h:366 [inline]
BUG: KASAN: stack-out-of-bounds in ax25_getname+0x4d/0x7b0 net/ax25/af_ax25.c:1405
Write of size 72 at addr ffff88807d117e20 by task syz-executor.2/11852

CPU: 0 PID: 11852 Comm: syz-executor.2 Not tainted 5.6.0-rc1-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
 print_address_description.constprop.8.cold.10+0x9/0x31d mm/kasan/report.c:374
 __kasan_report.cold.11+0x1b/0x32 mm/kasan/report.c:506
 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
 memset+0x23/0x40 mm/kasan/common.c:108
 memset include/linux/string.h:366 [inline]
 ax25_getname+0x4d/0x7b0 net/ax25/af_ax25.c:1405
 get_raw_socket drivers/vhost/net.c:1433 [inline]
 get_socket drivers/vhost/net.c:1489 [inline]
 vhost_net_set_backend drivers/vhost/net.c:1524 [inline]
 vhost_net_ioctl+0xe7e/0x1530 drivers/vhost/net.c:1715
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0xc1/0x110 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:770
 do_syscall_64+0xca/0x5f0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a639
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:00007f37dcb45c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a639
RDX: 0000000020d7c000 RSI: 000000004008af30 RDI: 0000000000000003
RBP: 000000000075c118 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f37dcb466d4
R13: 00000000004c5b18 R14: 00000000004dab78 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea0001f445c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x1fffc0000000000()
raw: 01fffc0000000000 0000000000000000 ffffea0001f445c8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

addr ffff88807d117e20 is located in stack of task syz-executor.2/11852 at offset 160 in frame:
 vhost_net_ioctl+0x0/0x1530 drivers/vhost/net.c:1245

this frame has 3 objects:
 [32, 36) 'r'
 [96, 104) 'backend'
 [160, 212) 'uaddr'

Memory state around the buggy address:
 ffff88807d117d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88807d117d80: f1 f1 f1 f1 04 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2
>ffff88807d117e00: f2 f2 f2 f2 00 00 00 00 00 00 04 f2 00 00 00 00
                                                 ^
 ffff88807d117e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88807d117f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================