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BUG: KASAN: use-after-free in memset include/linux/string.h:337 [inline]
BUG: KASAN: use-after-free in __ext4_expand_extra_isize+0x16c/0x240 fs/ext4/inode.c:5923
Write of size 4064 at addr ffff888079ed31a0 by task syz-executor3/8078

CPU: 1 PID: 8078 Comm: syz-executor3 Not tainted 5.0.0-rc3+ #40
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+0x1db/0x2d0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
 kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x123/0x190 mm/kasan/generic.c:191
 memset+0x24/0x40 mm/kasan/common.c:113
 memset include/linux/string.h:337 [inline]
 __ext4_expand_extra_isize+0x16c/0x240 fs/ext4/inode.c:5923
 ext4_try_to_expand_extra_isize fs/ext4/inode.c:5975 [inline]
 ext4_mark_inode_dirty+0x827/0xb80 fs/ext4/inode.c:6051
 ext4_dirty_inode+0x8f/0xc0 fs/ext4/inode.c:6085
 __mark_inode_dirty+0xab5/0x1590 fs/fs-writeback.c:2122
 generic_update_time+0x268/0x440 fs/inode.c:1654
 update_time fs/inode.c:1670 [inline]
 touch_atime+0x2a4/0x320 fs/inode.c:1741
 get_link fs/namei.c:1057 [inline]
 trailing_symlink+0x2d4/0x970 fs/namei.c:2263
 path_mountpoint+0x9ee/0x21a0 fs/namei.c:2696
 filename_mountpoint+0x258/0x490 fs/namei.c:2717
 user_path_mountpoint_at+0x3a/0x50 fs/namei.c:2747
 ksys_umount+0x198/0x1340 fs/namespace.c:1643
 __do_sys_umount fs/namespace.c:1669 [inline]
 __se_sys_umount fs/namespace.c:1667 [inline]
 __x64_sys_umount+0x54/0x80 fs/namespace.c:1667
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45aae7
Code: 44 00 00 b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 0d 8d fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 ed 8c fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc8e714918 EFLAGS: 00000202 ORIG_RAX: 00000000000000a6
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000045aae7
RDX: 0000000000402eb0 RSI: 0000000000000002 RDI: 00007ffc8e7149c0
RBP: 000000000000060a R08: 0000000000000000 R09: 0000000000000010
R10: 000000000000000a R11: 0000000000000202 R12: 00007ffc8e715a50
R13: 00000000015fd940 R14: 0000000000000000 R15: 0000000000000003

The buggy address belongs to the page:
page:ffffea0001e7b4c0 count:2 mapcount:0 mapping:ffff88821a181518 index:0x447
def_blk_aops 
flags: 0x1fffc000000203a(referenced|dirty|lru|active|private)
raw: 01fffc000000203a ffffea000203adc8 ffffea00020a2208 ffff88821a181518
raw: 0000000000000447 ffff88808d296888 00000002ffffffff ffff8880860e2d00
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8880860e2d00

Memory state around the buggy address:
 ffff888079ed3f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888079ed3f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888079ed4000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888079ed4080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888079ed4100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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