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Date:   Mon, 26 Nov 2018 12:39:05 -0800
From:   syzbot <>
Subject: WARNING in ext4_dio_get_block_overwrite


syzbot found the following crash on:

HEAD commit:    442b8cea2477 Add linux-next specific files for 20181109
git tree:       linux-next
console output:
kernel config:
dashboard link:
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:

audit: type=1804 audit(1543213093.902:156): pid=10653 uid=0 auid=4294967295  
ses=4294967295 subj==unconfined op=invalid_pcr cause=ToMToU  
name="/root/syzkaller-testdir952476403/syzkaller.2X9ByG/94/bus" dev="sda1"  
ino=16843 res=1
WARNING: CPU: 0 PID: 10648 at fs/ext4/inode.c:945  
ext4_dio_get_block_overwrite+0xbf/0x100 fs/ext4/inode.c:945
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 10648 Comm: syz-executor3 Not tainted 4.20.0-rc1-next-20181109+  
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+0x244/0x39d lib/dump_stack.c:113
  panic+0x2ad/0x55c kernel/panic.c:188
  __warn.cold.8+0x20/0x45 kernel/panic.c:540
  report_bug+0x254/0x2d0 lib/bug.c:186
  fixup_bug arch/x86/kernel/traps.c:178 [inline]
  do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
  do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
RIP: 0010:ext4_dio_get_block_overwrite+0xbf/0x100 fs/ext4/inode.c:945
Code: ff 48 85 db 74 1f e8 80 b0 64 ff 49 8b 1c 24 31 ff 48 c1 eb 0c 83 e3  
01 48 89 de e8 9b b1 64 ff 48 85 db 74 07 e8 61 b0 64 ff <0f> 0b e8 5a b0  
64 ff 44 89 e8 5b 41 5c 41 5d 41 5e 5d c3 e8 49 b0
RSP: 0018:ffff880179a0dc98 EFLAGS: 00010246
RAX: 0000000000040000 RBX: 0000000000000000 RCX: ffffc9000c02a000
RDX: 0000000000040000 RSI: ffffffff821af84f RDI: 0000000000000007
RBP: ffff880179a0dcb8 R08: ffff8801d203e3c0 R09: ffffed002e9db6a9
R10: ffffed002e9db6a9 R11: ffff880174edb54f R12: ffff880179a0e980
R13: 0000000000000000 R14: 000000000000006b R15: ffff880179a0ea20
  get_more_blocks fs/direct-io.c:716 [inline]
  do_direct_IO+0x1941/0xc110 fs/direct-io.c:1001
  do_blockdev_direct_IO+0x131e/0xa340 fs/direct-io.c:1333
  __blockdev_direct_IO+0x9d/0xc6 fs/direct-io.c:1419
  ext4_direct_IO_write fs/ext4/inode.c:3774 [inline]
  ext4_direct_IO+0x15ab/0x2220 fs/ext4/inode.c:3901
  generic_file_direct_write+0x275/0x4b0 mm/filemap.c:3043
  __generic_file_write_iter+0x2ff/0x630 mm/filemap.c:3222
  ext4_file_write_iter+0x390/0x1420 fs/ext4/file.c:266
  call_write_iter include/linux/fs.h:1867 [inline]
  do_iter_readv_writev+0x8b0/0xa80 fs/read_write.c:680
  do_iter_write+0x185/0x5f0 fs/read_write.c:959
  vfs_iter_write+0x77/0xb0 fs/read_write.c:972
  iter_file_splice_write+0x90d/0x1050 fs/splice.c:749
  do_splice_from fs/splice.c:851 [inline]
  direct_splice_actor+0x128/0x190 fs/splice.c:1018
  splice_direct_to_actor+0x318/0x8f0 fs/splice.c:973
  do_splice_direct+0x2d4/0x420 fs/splice.c:1061
  do_sendfile+0x62a/0xe20 fs/read_write.c:1439
  __do_sys_sendfile64 fs/read_write.c:1500 [inline]
  __se_sys_sendfile64 fs/read_write.c:1486 [inline]
  __x64_sys_sendfile64+0x1fd/0x250 fs/read_write.c:1486
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
RIP: 0033:0x457569
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f2cc2bb1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000457569
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000005
RBP: 000000000072bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000a5cc54d R11: 0000000000000246 R12: 00007f2cc2bb26d4
R13: 00000000004c3c2a R14: 00000000004d63d0 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..

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