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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:5921
Write of size 8490 at addr ffff8880269da0a0 by task syz-executor.5/14467

CPU: 1 PID: 14467 Comm: syz-executor.5 Not tainted 5.0.0-rc6-next-20190213 #34
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.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:115
 memset include/linux/string.h:337 [inline]
 __ext4_expand_extra_isize+0x16c/0x240 fs/ext4/inode.c:5921
 ext4_try_to_expand_extra_isize fs/ext4/inode.c:5973 [inline]
 ext4_mark_inode_dirty+0x6e9/0x940 fs/ext4/inode.c:6049
 ext4_evict_inode+0x978/0x18f0 fs/ext4/inode.c:282
 evict+0x309/0x680 fs/inode.c:558
 iput_final fs/inode.c:1547 [inline]
 iput+0x530/0x8d0 fs/inode.c:1573
 dentry_unlink_inode+0x2dc/0x3a0 fs/dcache.c:374
 __dentry_kill+0x390/0x610 fs/dcache.c:579
 dentry_kill+0xd7/0x5e0 fs/dcache.c:698
 dput+0x570/0x6a0 fs/dcache.c:859
 __fput+0x42f/0x8d0 fs/file_table.c:291
 ____fput+0x16/0x20 fs/file_table.c:309
 task_work_run+0x14a/0x1c0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x90a/0x2fa0 kernel/exit.c:876
 do_group_exit+0x135/0x370 kernel/exit.c:980
 get_signal+0x35c/0x1d60 kernel/signal.c:2574
 do_signal+0x87/0x1940 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457e29
Code: ad b8 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 b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f5a2dbdbcf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000073bf08 RCX: 0000000000457e29
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000073bf08
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000073bf0c
R13: 00007ffec485aedf R14: 00007f5a2dbdc9c0 R15: 000000000073bf0c

The buggy address belongs to the page:
page:ffffea00009a7680 count:2 mapcount:0 mapping:ffff88819d4b2558 index:0x496
def_blk_aops 
flags: 0x1fffc0000002032(referenced|lru|active|private)
raw: 01fffc0000002032 ffffea000194e548 ffffea000294a448 ffff88819d4b2558
raw: 0000000000000496 ffff88808fda0c78 00000002ffffffff ffff888089140940
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff888089140940

Memory state around the buggy address:
 ffff8880269dbf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880269dbf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880269dc000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8880269dc080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880269dc100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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