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Commit 300c7d75 authored by Steven Whitehouse's avatar Steven Whitehouse
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[GFS2] Fix recursive locking in gfs2_permission 



Since gfs2_permission may be called either from the VFS (in which case
we need to obtain a shared glock) or from GFS2 (in which case we already
have a glock) we need to test to see whether or not a lock is required.
The original test was buggy due to a potential race. This one should
be safe.

This fixes Red Hat bugzilla #217129

Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent cb4c0313

fs/gfs2/ops_inode.c

+13 −6
Original line number Original line Diff line number Diff line
@@ -835,6 +835,10 @@ static void *gfs2_follow_link(struct dentry *dentry, struct nameidata *nd) 
 * @mask:

 * @mask:

 * @nd: passed from Linux VFS, ignored by us

 * @nd: passed from Linux VFS, ignored by us

 *

 *

 * This may be called from the VFS directly, or from within GFS2 with the

 * inode locked, so we look to see if the glock is already locked and only

 * lock the glock if its not already been done.

 *

 * Returns: errno

 * Returns: errno

 */

 */
@@ -843,15 +847,18 @@ static int gfs2_permission(struct inode *inode, int mask, struct nameidata *nd) 
	struct gfs2_inode *ip = GFS2_I(inode);

	struct gfs2_inode *ip = GFS2_I(inode);

	struct gfs2_holder i_gh;

	struct gfs2_holder i_gh;

	int error;

	int error;

	int unlock = 0;





	if (!test_bit(GIF_INVALID, &ip->i_flags))

	if (gfs2_glock_is_locked_by_me(ip->i_gl) == 0) {

		return generic_permission(inode, mask, gfs2_check_acl);



		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);

		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);

	if (!error) {

		if (error)

			return error;

		unlock = 1;

	}



	error = generic_permission(inode, mask, gfs2_check_acl_locked);

	error = generic_permission(inode, mask, gfs2_check_acl_locked);

	if (unlock)

		gfs2_glock_dq_uninit(&i_gh);

		gfs2_glock_dq_uninit(&i_gh);

	}





	return error;

	return error;

}

}