Re: NULL pointer dereference in ext4_superblock_csum_set withmounted filesystem

From: Josh Triplett
Date: Wed Mar 13 2013 - 15:10:28 EST


On Wed, Mar 13, 2013 at 03:01:41PM -0400, Theodore Ts'o wrote:
> On Wed, Mar 13, 2013 at 11:59:13AM -0700, Josh Triplett wrote:
> > I frequently test kernel changes by booting them with kvm's -kernel
> > option, with -hda pointing to my host system's root filesystem, and
> > -snapshot to prevent writing to (and likely corrupting) that root
> > filesystem. I tried this with a kernel built from git commit
> > 7c6baa304b841673d3a55ea4fcf9a5cbf7a1674b, with a stock x86-64 "make
> > defconfig", and got a kernel panic:
>
> Can you send me the output of "dumpe2fs -h" on your host system's root
> file system?

Attached.

- Josh Triplett
dumpe2fs 1.42.5 (29-Jul-2012)
Filesystem volume name: <none>
Last mounted on: /
Filesystem UUID: e23a62e0-8a4a-48d0-b781-e11ae069ab06
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: (none)
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 17711104
Block count: 70817792
Reserved block count: 708177
Free blocks: 50350508
Free inodes: 17149541
First block: 0
Block size: 4096
Fragment size: 4096
Reserved GDT blocks: 1007
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 8192
Inode blocks per group: 512
Flex block group size: 16
Filesystem created: Tue Jul 10 22:09:47 2012
Last mount time: Wed Mar 13 10:19:40 2013
Last write time: Wed Mar 13 10:19:40 2013
Mount count: 6
Maximum mount count: 27
Last checked: Mon Mar 11 21:27:56 2013
Check interval: 15552000 (6 months)
Next check after: Sat Sep 7 21:27:56 2013
Lifetime writes: 776 GB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
First orphan inode: 12845162
Default directory hash: half_md4
Directory Hash Seed: 22edf7ec-c22c-43aa-a7ea-c3349da9a00c
Journal backup: inode blocks
Journal features: journal_incompat_revoke
Journal size: 128M
Journal length: 32768
Journal sequence: 0x0023bba0
Journal start: 10041