syzbot

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kernel BUG at fs/ext4/inode.c:2474!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 5492 Comm: syz-executor950 Not tainted 4.4.140-ged9bdc8 #68
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b0720000 task.stack: ffff8800b1ac0000
RIP: 0010:[<ffffffff816d7fcf>]  [<ffffffff816d7fcf>] mpage_prepare_extent_to_map+0x74f/0x970 fs/ext4/inode.c:2474
RSP: 0000:ffff8800b1ac75e0  EFLAGS: 00010293
RAX: ffff8800b0720000 RBX: ffffea000284fbc0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff816d7fcf RDI: ffffea000284fbc8
RBP: ffff8800b1ac77a8 R08: ffff8800b0720928 R09: 0000000000000001
R10: 0000000000000000 R11: ffff8800b0720000 R12: 0000000000000003
R13: 0000000000000000 R14: ffff8800b1ac78f0 R15: dffffc0000000000
FS:  00007fb5e539b700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020d83ff8 CR3: 00000000b28df000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8800b1ac7708 1ffff10016358ecc ffff8800b1ac78f8 ffff8800b1ac7680
 ffff8800b1ac7900 00000000b657b3e8 ffff8800b9f0dbd8 000000070000000c
 7fffffffffffffff ffff8800b1ac76c0 ffff8800b1ac7908 ffffea000284fbd0
Call Trace:
 [<ffffffff816ea250>] ext4_writepages+0xbb0/0x2c80 fs/ext4/inode.c:2629
 [<ffffffff814401bf>] do_writepages+0xef/0x1d0 mm/page-writeback.c:2350
 [<ffffffff81422773>] __filemap_fdatawrite_range+0x1b3/0x250 mm/filemap.c:347
 [<ffffffff81422993>] __filemap_fdatawrite mm/filemap.c:355 [inline]
 [<ffffffff81422993>] filemap_flush+0x23/0x30 mm/filemap.c:380
 [<ffffffff816e0258>] ext4_alloc_da_blocks+0x108/0x3c0 fs/ext4/inode.c:3005
 [<ffffffff816c495f>] ext4_release_file+0x1ff/0x2e0 fs/ext4/file.c:42
 [<ffffffff81522e45>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81523385>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bdbf>] task_work_run+0x10f/0x190 kernel/task_work.c:115
 [<ffffffff8115f2b0>] get_signal+0x1190/0x14b0 kernel/signal.c:2151
 [<ffffffff8100df8b>] do_signal+0x8b/0x1d30 arch/x86/kernel/signal.c:712
 [<ffffffff8100360a>] exit_to_usermode_loop+0x11a/0x160 arch/x86/entry/common.c:248
 [<ffffffff81006535>] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline]
 [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:348
 [<ffffffff838c2935>] int_ret_from_sys_call+0x25/0xa3
Code: ff 48 8b 75 d0 65 48 33 34 25 28 00 00 00 0f 85 2e 02 00 00 48 81 c4 a0 01 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 21 95 c7 ff <0f> 0b e8 1a 95 c7 ff 8b 95 18 ff ff ff 85 d2 75 7f e8 0b 95 c7 
RIP  [<ffffffff816d7fcf>] mpage_prepare_extent_to_map+0x74f/0x970 fs/ext4/inode.c:2474
 RSP <ffff8800b1ac75e0>
---[ end trace b96ac62b23be201d ]---