==================================================================
BUG: KASAN: use-after-free in memset include/linux/string.h:410 [inline]
BUG: KASAN: use-after-free in __ext4_expand_extra_isize+0x1ab/0x290 fs/ext4/inode.c:5581
Write of size 8160 at addr ffff8880929863a0 by task syz-executor.0/8813

CPU: 0 PID: 8813 Comm: syz-executor.0 Not tainted 5.4.0-rc6-next-20191107 #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+0x197/0x210 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:634
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
 memset+0x24/0x40 mm/kasan/common.c:105
 memset include/linux/string.h:410 [inline]
 __ext4_expand_extra_isize+0x1ab/0x290 fs/ext4/inode.c:5581
 ext4_try_to_expand_extra_isize fs/ext4/inode.c:5632 [inline]
 ext4_mark_inode_dirty+0x74e/0x9c0 fs/ext4/inode.c:5708
 ext4_unlink fs/ext4/namei.c:3209 [inline]
 ext4_unlink+0xd26/0x1120 fs/ext4/namei.c:3154
 vfs_unlink+0x2d7/0x620 fs/namei.c:3995
 do_unlinkat+0x3f7/0x6d0 fs/namei.c:4059
 __do_sys_unlink fs/namei.c:4106 [inline]
 __se_sys_unlink fs/namei.c:4104 [inline]
 __x64_sys_unlink+0x42/0x50 fs/namei.c:4104
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459f67
Code: 00 66 90 b8 58 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 4d b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 57 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 2d b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffe556abc28 EFLAGS: 00000246 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000459f67
RDX: 00007ffe556abc40 RSI: 00007ffe556abc40 RDI: 00007ffe556abcd0
RBP: 000000000000048f R08: 0000000000000000 R09: 000000000000000c
R10: 0000000000000006 R11: 0000000000000246 R12: 00007ffe556acd60
R13: 0000000001955940 R14: 0000000000000000 R15: 00007ffe556acd60

The buggy address belongs to the page:
page:ffffea00024a6180 refcount:2 mapcount:0 mapping:ffff88821a3ebb20 index:0x428
def_blk_aops 
flags: 0x1fffc000000203a(referenced|dirty|lru|active|private)
raw: 01fffc000000203a ffffea00024070c8 ffffea0002911788 ffff88821a3ebb20
raw: 0000000000000428 ffff88808f6e5348 00000002ffffffff ffff8880a9832000
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8880a9832000

Memory state around the buggy address:
 ffff888092987f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888092987f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888092988000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888092988080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888092988100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================