==================================================================
BUG: KASAN: use-after-free in memset include/linux/string.h:332 [inline]
BUG: KASAN: use-after-free in __ext4_expand_extra_isize+0x14f/0x220 fs/ext4/inode.c:5754
Write of size 19509 at addr ffff88808a1a96a0 by task syz-executor.4/9108

CPU: 0 PID: 9108 Comm: syz-executor.4 Not tainted 4.14.146 #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+0x138/0x197 lib/dump_stack.c:53
 print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x123/0x190 mm/kasan/kasan.c:267
 memset+0x24/0x40 mm/kasan/kasan.c:285
 memset include/linux/string.h:332 [inline]
 __ext4_expand_extra_isize+0x14f/0x220 fs/ext4/inode.c:5754
 ext4_try_to_expand_extra_isize fs/ext4/inode.c:5806 [inline]
 ext4_mark_inode_dirty+0x664/0x860 fs/ext4/inode.c:5882
 ext4_unlink fs/ext4/namei.c:3083 [inline]
 ext4_unlink+0xae0/0xe90 fs/ext4/namei.c:3023
 vfs_unlink+0x281/0x480 fs/namei.c:4024
 do_unlinkat+0x33d/0x600 fs/namei.c:4089
 SYSC_unlink fs/namei.c:4136 [inline]
 SyS_unlink+0x1b/0x20 fs/namei.c:4134
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459777
RSP: 002b:00007ffc29b49a28 EFLAGS: 00000246 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000459777
RDX: 00007ffc29b49a40 RSI: 00007ffc29b49a40 RDI: 00007ffc29b49ad0
RBP: 000000000000002e R08: 0000000000000000 R09: 000000000000000f
R10: 000000000000000a R11: 0000000000000246 R12: 00007ffc29b4ab60
R13: 00005555566ab940 R14: 0000000000000000 R15: 00007ffc29b4ab60

The buggy address belongs to the page:
page:ffffea0002286a40 count:2 mapcount:0 mapping:ffff8882184275a0 index:0x42b
flags: 0x1fffc0000001074(referenced|dirty|lru|active|private)
raw: 01fffc0000001074 ffff8882184275a0 000000000000042b 00000002ffffffff
raw: ffffea00017fa1a0 ffffea0002263860 ffff888076cff0a8 ffff88821b7321c0
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff88821b7321c0

Memory state around the buggy address:
 ffff88808a1abf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88808a1abf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88808a1ac000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88808a1ac080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88808a1ac100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
audit: type=1800 audit(1570007340.546:77): pid=6805 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed" comm="rsyslogd" name="libgcc_s.so.1" dev="sda1" ino=2665 res=0