Re: [PATCH] btrfs-progs: add stat check in open_ctree_fs_info

["Austin S. Hemmelgarn" <ahferroin7@gmail.com>]

On 2016-03-17 04:58, Duncan wrote:
> Austin S. Hemmelgarn posted on Wed, 16 Mar 2016 11:26:11 -0400 as
> excerpted:
>
>> Currently, open_ctree_fs_info will open whatever path you pass it and
>> try to interpret it as a BTRFS filesystem.  While this is not
>> nessecarily dangerous (except possibly if done on a character device),
>> it does result in some rather cryptic and non-sensical error messages
>> when trying to run certain commands in ways they weren't intended to be
>> run.  Add a check using stat(2) to verify that the path we've been
>> passed is in fact a regular file or a block device.
>>
>> This causes the following commands to provide a helpful error message
>> when run on a FIFO, directory, character device, or socket:
>
> Umm... what about a symlink?  A symlink isn't a block device or regular
> file, but obviously with udev, symlinks to block devices /better/ work.
> Do you dereference symlinks before doing this check?
>
>
I'm using stat(2) instead of lstat(2), and stat(2) dereferences symlinks 
just like open(2) does, so I shouldn't have to dereference them 
manually.  That said, I did check that it works with symlinks to both 
block devices and regular files, and everything appears to work correctly.