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

[Ian Kent]

On 21/9/22 09:20, Theodore Ts'o wrote:
> 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?

Hi Ted,


I suppose but it seems to me that, for certain file systems, mostly

pseudo file systems, the source isn't needed and is left out ... so

disallowing a zero length source could lead to quite a bit of breakage.


Ian