Re: [PATCH][RFC][resend] potential NULL pointer deref in XFS on failed mount

[Shailendra Tripathi <stripathi@xxxxxxxxx>]

Jesper Juhl wrote:

> The reason I want to fix it in the freeing function is that many other
> functions in the kernel that free resources are safe to call with NULL
> pointers and this would make xfs_free_buftarg() follow that
> convention.  This would perhaps also allow for some cleanups in other
> places that call the function since then there's no longer a need for
> explicit NULL checks any more (haven't checked if there's anything to
> gain there though).
> I don't think the function call overhead matters much since this is in
> a case of a failed mount, so it should happen very rarely.
I agree with you.  However, cleanup functions should(/must?) check for  
NULL etc and
in this case it is already doing so for other cases. So, perhaps not 
required. Just a different viewpoint.
Your choice.

> > void
> > xfs_unmountfs_close(xfs_mount_t *mp, struct cred *cr)
> > {
> >        if (mp->m_logdev_targp && (mp->m_logdev_targp != 
> > mp->m_ddev_targp))
> >                 xfs_free_buftarg(mp->m_logdev_targp, 1);
> >         if (mp->m_rtdev_targp)
> >                 xfs_free_buftarg(mp->m_rtdev_targp, 1);
> >         xfs_free_buftarg(mp->m_ddev_targp, 0);
> > }