[PATCH 2/2] xfs: kill suid/sgid through the truncate path.

[Christoph Hellwig]

On Fri, May 24, 2013 at 06:58:08PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner at redhat.com>
> 
> XFS has failed to kill suid/sgid bits correctly when truncating
> files of non-zero size since commit c4ed4243 ("xfs: split
> xfs_setattr") introduced in the 3.1 kernel. Fix it.

This should get a testcase in xfstests.

> +xfs_setattr_mode(
> +	struct inode	*inode,
> +	struct iattr	*iattr)
> +{
> +	struct xfs_inode *ip = XFS_I(inode);
> +	umode_t		mode = iattr->ia_mode;
> +
> +	if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
> +		mode &= ~S_ISGID;
> +
> +	ip->i_d.di_mode &= S_IFMT;
> +	ip->i_d.di_mode |= mode & ~S_IFMT;
> +
> +	inode->i_mode &= S_IFMT;
> +	inode->i_mode |= mode & ~S_IFMT;

This function should have assers that the xfs_inode is locked
exclusively and joined to a transaction.