btrfs device stats /dev/mapper/ext4 SEGV

btrfs device stats /dev/mapper/ext4 SEGV

[Russell Coker]

http://git.kernel.org/?p=linux/kernel/git/mason/btrfs-progs.git

I can repeatedly get the following SEGV from running "btrfs device stats" on a 
device node for an Ext3/4 filesystem.  This happens with the version of the 
code downloaded from the above GIT repository as well as with an older 
version.  Obviously the command in question is not going to do anything useful 
when run against a non-BTRFS filesystem, but it should do something other than 
crash.

Program received signal SIGSEGV, Segmentation fault.
0x000000000045842d in get_fs_info (path=0x7fffffffce60 "/boot", 
    fi_args=0x7fffffffe6c0, di_ret=0x7fffffffe6b8) at utils.c:1560
1560                    fi_args->max_id = fs_devices_mnt->latest_devid;
(gdb) bt
#0  0x000000000045842d in get_fs_info (path=0x7fffffffce60 "/boot", 
    fi_args=0x7fffffffe6c0, di_ret=0x7fffffffe6b8) at utils.c:1560
#1  0x0000000000408576 in cmd_dev_stats (argc=2, argv=0x7fffffffec78)
    at cmds-device.c:331
#2  0x0000000000404177 in handle_command_group (grp=0x684660, argc=2, 
    argv=0x7fffffffec78) at btrfs.c:154
#3  0x0000000000408830 in cmd_device (argc=3, argv=0x7fffffffec70)
    at cmds-device.c:410
#4  0x000000000040450e in main (argc=3, argv=0x7fffffffec70) at btrfs.c:296

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Re: btrfs device stats /dev/mapper/ext4 SEGV

[Chris Samuel]

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On Sat, 10 Aug 2013 07:07:50 PM Russell Coker wrote:

> I can repeatedly get the following SEGV from running "btrfs device stats" on
> a  device node for an Ext3/4 filesystem.  This happens with the version of
> the code downloaded from the above GIT repository as well as with an older
> version.  Obviously the command in question is not going to do anything
> useful when run against a non-BTRFS filesystem, but it should do something
> other than crash.

The code calls btrfs_read_dev_super() on that filesystem, but it looks like the 
checks are failing to detect it as not btrfs.  :-(

I can reproduce the crash here too with ext3 and XFS filesystems.

-- 
 Chris Samuel  :  http://www.csamuel.org/  :  Melbourne, VIC

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Re: btrfs device stats /dev/mapper/ext4 SEGV

[Anand Jain]

On 08/10/2013 09:56 PM, Chris Samuel wrote:
> On Sat, 10 Aug 2013 07:07:50 PM Russell Coker wrote:
>
>> I can repeatedly get the following SEGV from running "btrfs device stats" on
>> a  device node for an Ext3/4 filesystem.  This happens with the version of
>> the code downloaded from the above GIT repository as well as with an older
>> version.  Obviously the command in question is not going to do anything
>> useful when run against a non-BTRFS filesystem, but it should do something
>> other than crash.
>
> The code calls btrfs_read_dev_super() on that filesystem, but it looks like the
> checks are failing to detect it as not btrfs.  :-(
>
> I can reproduce the crash here too with ext3 and XFS filesystems.

  There are quite a number of bug similar to this (that was
  reported to the mainling list here, but hard to search now)
  which is all triggered by using the backup super block invariably.


  v6: access to backup superblock
  http://permalink.gmane.org/gmane.comp.file-systems.btrfs/24746

  provided fix. But it needs rebase, if you could
  goback in git this patch might apply nicely for testing.

Thanks, Anand