WARNING in get_unlocked_entry

From: syzbot
Date: Tue Oct 30 2018 - 11:00:21 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 4b42745211af Merge tag 'armsoc-soc' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1187d06d400000
kernel config: https://syzkaller.appspot.com/x/.config?x=93932074d01b4a5
dashboard link: https://syzkaller.appspot.com/bug?extid=4fd0c066d82852499145
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:
Reported-by: syzbot+4fd0c066d82852499145@xxxxxxxxxxxxxxxxxxxxxxxxx

EXT4-fs (sda1): Cannot specify journal on remount
EXT4-fs (sda1): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
EXT4-fs (sda1): warning: refusing change of dax flag with busy inodes while remounting
WARNING: CPU: 0 PID: 12870 at fs/dax.c:227 get_unlocked_entry+0x3ac/0x4d0 fs/dax.c:227
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 12870 Comm: syz-executor3 Not tainted 4.19.0+ #87
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+0x238/0x4e7 kernel/panic.c:184
__warn.cold.8+0x20/0x4a kernel/panic.c:536
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:966
RIP: 0010:get_unlocked_entry+0x3ac/0x4d0 fs/dax.c:227
Code: e8 31 ff 83 e0 01 48 89 c6 48 89 85 10 ff ff ff e8 09 18 96 ff 48 8b 85 10 ff ff ff 48 85 c0 0f 85 34 fe ff ff e8 c4 16 96 ff <0f> 0b e8 bd 16 96 ff 48 b8 00 00 00 00 00 fc ff df 48 03 85 f8 fe
RSP: 0018:ffff88018025e7b8 EFLAGS: 00010012
RAX: 0000000000040000 RBX: ffff88018025ead8 RCX: ffffc90008983000
RDX: 0000000000000341 RSI: ffffffff81e94d3c RDI: 0000000000000007
RBP: ffff88018025e8c8 R08: ffff88017f862280 R09: ffffed003004bd08
R10: ffffed003004bd08 R11: 0000000000000003 R12: dffffc0000000000
R13: ffffea0005e01040 R14: ffff88018025e800 R15: ffff88018025e8a0
grab_mapping_entry fs/dax.c:447 [inline]
dax_iomap_pte_fault.isra.35+0x8a5/0x37c0 fs/dax.c:1239
dax_iomap_fault+0x51/0x70 fs/dax.c:1600
ext4_dax_huge_fault+0x565/0x730 fs/ext4/file.c:320
ext4_dax_fault+0x17/0x20 fs/ext4/file.c:341
__do_fault+0x100/0x6b0 mm/memory.c:2991
do_cow_fault mm/memory.c:3432 [inline]
do_fault mm/memory.c:3531 [inline]
handle_pte_fault mm/memory.c:3760 [inline]
__handle_mm_fault+0x141b/0x5be0 mm/memory.c:3884
handle_mm_fault+0x54f/0xc70 mm/memory.c:3921
do_user_addr_fault arch/x86/mm/fault.c:1423 [inline]
__do_page_fault+0x5e8/0xe60 arch/x86/mm/fault.c:1489
do_page_fault+0xf2/0x7e0 arch/x86/mm/fault.c:1520
page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1136
RIP: 0010:copy_user_generic_unrolled+0x89/0xc0 arch/x86/lib/copy_user_64.S:66
Code: 38 4c 89 47 20 4c 89 4f 28 4c 89 57 30 4c 89 5f 38 48 8d 76 40 48 8d 7f 40 ff c9 75 b6 89 d1 83 e2 07 c1 e9 03 74 12 4c 8b 06 <4c> 89 07 48 8d 76 08 48 8d 7f 08 ff c9 75 ee 21 d2 74 10 89 d1 8a
RSP: 0018:ffff88018025f7d0 EFLAGS: 00010207
RAX: 0000000000000004 RBX: 000000000000001c RCX: 0000000000000003
RDX: 0000000000000004 RSI: ffff88018025fb40 RDI: 0000000020000000
RBP: ffff88018025f808 R08: 00000000000000b8 R09: ffffed003004bf68
R10: ffffed003004bf6b R11: 0000000000000003 R12: 000000002000001c
R13: 0000000020000000 R14: ffff88018025fb40 R15: 00007ffffffff000
copy_to_user include/linux/uaccess.h:155 [inline]
ext4_ioctl+0x3ed/0x44c0 fs/ext4/ioctl.c:1035
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
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:00007f0efb87dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457569
RDX: 0000000020000000 RSI: 00000000801c581f RDI: 0000000000000003
RBP: 000000000072c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f0efb87e6d4
R13: 00000000004bf929 R14: 00000000004cfa80 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..

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Next message: Rob Herring: "Re: [PATCH 01/21] of: Add cpu node iterator for_each_of_cpu_node()"
Previous message: syzbot: "KASAN: slab-out-of-bounds Read in _decode_session6 (2)"
Next in thread: Matthew Wilcox: "Re: WARNING in get_unlocked_entry"
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