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BUG: KASAN: use-after-free in memset include/linux/string.h:389 [inline]
BUG: KASAN: use-after-free in __ext4_expand_extra_isize+0x1ab/0x290 fs/ext4/inode.c:5924
Write of size 736 at addr ffff888010c9cea0 by task syz-executor.3/18331

CPU: 1 PID: 18331 Comm: syz-executor.3 Not tainted 5.4.0-rc1-next-20191004 #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+0x172/0x1f0 lib/dump_stack.c:113
 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:389 [inline]
 __ext4_expand_extra_isize+0x1ab/0x290 fs/ext4/inode.c:5924
 ext4_try_to_expand_extra_isize fs/ext4/inode.c:5976 [inline]
 ext4_mark_inode_dirty+0x74e/0x9b0 fs/ext4/inode.c:6052
 ext4_evict_inode+0x977/0x14e0 fs/ext4/inode.c:282
 evict+0x306/0x680 fs/inode.c:574
 iput_final fs/inode.c:1563 [inline]
 iput+0x55d/0x900 fs/inode.c:1589
 dentry_unlink_inode+0x2d9/0x400 fs/dcache.c:374
 __dentry_kill+0x38b/0x600 fs/dcache.c:579
 dentry_kill fs/dcache.c:698 [inline]
 dput+0x639/0xe10 fs/dcache.c:859
 path_put+0x31/0x70 fs/namei.c:482
 free_fs_struct+0x25/0x70 fs/fs_struct.c:91
 exit_fs+0xf0/0x130 fs/fs_struct.c:108
 do_exit+0x8da/0x2e60 kernel/exit.c:813
 do_group_exit+0x135/0x360 kernel/exit.c:921
 get_signal+0x47c/0x2500 kernel/signal.c:2734
 do_signal+0x87/0x1700 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x286/0x380 arch/x86/entry/common.c:159
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x65f/0x760 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459a59
Code: Bad RIP value.
RSP: 002b:00007fb28c77ecf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000075bfd0 RCX: 0000000000459a59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000075bfd0
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000075bfd4
R13: 00007ffe8c22ecbf R14: 00007fb28c77f9c0 R15: 000000000075bfd4

The buggy address belongs to the page:
page:ffffea0000432700 refcount:2 mapcount:0 mapping:ffff888219f05520 index:0x42e
def_blk_aops 
flags: 0x1fffc000000203a(referenced|dirty|lru|active|private)
raw: 01fffc000000203a ffffea000055d848 ffffea000202da48 ffff888219f05520
raw: 000000000000042e ffff88803994b2a0 00000002ffffffff ffff888096326000
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff888096326000

Memory state around the buggy address:
 ffff888010c9cf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888010c9cf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888010c9d000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888010c9d080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888010c9d100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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