Commit 1d6757fb authored by Trond Myklebust's avatar Trond Myklebust Committed by Linus Torvalds
Browse files

[PATCH] NFS: Fix lookup intent handling 



We should never apply a lookup intent to anything other than the last
path component in an open(), create() or access() call.

Introduce the helper nfs_lookup_check_intent() which always returns
zero if LOOKUP_CONTINUE or LOOKUP_PARENT are set, and returns the
intent flags if we're on the last component of the lookup.
By doing so, we fix a bug in open(O_EXCL), where we may end up
optimizing away a real lookup of the parent directory.

Problem noticed by Linda Dunaphant <linda.dunaphant@ccur.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent eba4f669

fs/nfs/dir.c

+35 −14
Original line number Diff line number Diff line
@@ -528,19 +528,39 @@ static inline void nfs_renew_times(struct dentry * dentry) 
	dentry->d_time = jiffies;

}



/*

 * Return the intent data that applies to this particular path component

 *

 * Note that the current set of intents only apply to the very last

 * component of the path.

 * We check for this using LOOKUP_CONTINUE and LOOKUP_PARENT.

 */

static inline unsigned int nfs_lookup_check_intent(struct nameidata *nd, unsigned int mask)

{

	if (nd->flags & (LOOKUP_CONTINUE|LOOKUP_PARENT))

		return 0;

	return nd->flags & mask;

}



/*

 * Inode and filehandle revalidation for lookups.

 *

 * We force revalidation in the cases where the VFS sets LOOKUP_REVAL,

 * or if the intent information indicates that we're about to open this

 * particular file and the "nocto" mount flag is not set.

 *

 */

static inline

int nfs_lookup_verify_inode(struct inode *inode, struct nameidata *nd)

{

	struct nfs_server *server = NFS_SERVER(inode);



	if (nd != NULL) {

		int ndflags = nd->flags;

		/* VFS wants an on-the-wire revalidation */

		if (ndflags & LOOKUP_REVAL)

		if (nd->flags & LOOKUP_REVAL)

			goto out_force;

		/* This is an open(2) */

		if ((ndflags & LOOKUP_OPEN) &&

				!(ndflags & LOOKUP_CONTINUE) &&

		if (nfs_lookup_check_intent(nd, LOOKUP_OPEN) != 0 &&

				!(server->flags & NFS_MOUNT_NOCTO))

			goto out_force;

	}
@@ -560,12 +580,8 @@ static inline 
int nfs_neg_need_reval(struct inode *dir, struct dentry *dentry,

		       struct nameidata *nd)

{

	int ndflags = 0;



	if (nd)

		ndflags = nd->flags;

	/* Don't revalidate a negative dentry if we're creating a new file */

	if ((ndflags & LOOKUP_CREATE) && !(ndflags & LOOKUP_CONTINUE))

	if (nd != NULL && nfs_lookup_check_intent(nd, LOOKUP_CREATE) != 0)

		return 0;

	return !nfs_check_verifier(dir, dentry);

}
@@ -700,12 +716,16 @@ struct dentry_operations nfs_dentry_operations = { 
	.d_iput		= nfs_dentry_iput,

};



/*

 * Use intent information to check whether or not we're going to do

 * an O_EXCL create using this path component.

 */

static inline

int nfs_is_exclusive_create(struct inode *dir, struct nameidata *nd)

{

	if (NFS_PROTO(dir)->version == 2)

		return 0;

	if (!nd || (nd->flags & LOOKUP_CONTINUE) || !(nd->flags & LOOKUP_CREATE))

	if (nd == NULL || nfs_lookup_check_intent(nd, LOOKUP_CREATE) == 0)

		return 0;

	return (nd->intent.open.flags & O_EXCL) != 0;

}
@@ -772,12 +792,13 @@ struct dentry_operations nfs4_dentry_operations = { 
	.d_iput		= nfs_dentry_iput,

};



/*

 * Use intent information to determine whether we need to substitute

 * the NFSv4-style stateful OPEN for the LOOKUP call

 */

static int is_atomic_open(struct inode *dir, struct nameidata *nd)

{

	if (!nd)

		return 0;

	/* Check that we are indeed trying to open this file */

	if ((nd->flags & LOOKUP_CONTINUE) || !(nd->flags & LOOKUP_OPEN))

	if (nd == NULL || nfs_lookup_check_intent(nd, LOOKUP_OPEN) == 0)

		return 0;

	/* NFS does not (yet) have a stateful open for directories */

	if (nd->flags & LOOKUP_DIRECTORY)

CRA Git | Maintained and supported by SUSTech CRA and CCSE