Re: [REPOST PATCH v3 0/2] vfs: fix a mount table handling problem

[Theodore Ts'o]

On Tue, Sep 20, 2022 at 03:26:17PM +0800, Ian Kent wrote:
> Whenever a mount has an empty "source" (aka mnt_fsname), the glibc
> function getmntent incorrectly parses its input, resulting in reporting
> incorrect data to the caller.
> 
> The problem is that the get_mnt_entry() function in glibc's
> misc/mntent_r.c assumes that leading whitespace on a line can always
> be discarded because it will always be followed by a # for the case
> of a comment or a non-whitespace character that's part of the value
> of the first field. However, this assumption is violated when the
> value of the first field is an empty string.
> 
> This is fixed in the mount API code by simply checking for a pointer
> that contains a NULL and treating it as a NULL pointer.

Why not simply have the mount API code disallow a zero-length "source"
/ mnt_fsname?

					- Ted