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Commit 16c2cd71 authored by Al Viro's avatar Al Viro
Browse files

untangle the "need_reval_dot" mess 



instead of ad-hackery around need_reval_dot(), do the following:
set a flag (LOOKUP_JUMPED) in the beginning of path, on absolute
symlink traversal, on ".." and on procfs-style symlinks.  Clear on
normal components, leave unchanged on ".".  Non-nested callers of
link_path_walk() call handle_reval_path(), which checks that flag
is set and that fs does want the final revalidate thing, then does
->d_revalidate().  In link_path_walk() all the return_reval stuff
is gone.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent fe479a58

fs/namei.c

+44 −63
Original line number Diff line number Diff line
@@ -613,19 +613,8 @@ do_revalidate_rcu(struct dentry *dentry, struct nameidata *nd) 
	return dentry;

}



static inline int need_reval_dot(struct dentry *dentry)

{

	if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))

		return 0;



	if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))

		return 0;



	return 1;

}



/*

 * force_reval_path - force revalidation of a dentry

 * handle_reval_path - force revalidation of a dentry

 *

 * In some situations the path walking code will trust dentries without

 * revalidating them. This causes problems for filesystems that depend on
@@ -639,27 +628,28 @@ static inline int need_reval_dot(struct dentry *dentry) 
 * invalidate the dentry. It's up to the caller to handle putting references

 * to the path if necessary.

 */

static int

force_reval_path(struct path *path, struct nameidata *nd)

static inline int handle_reval_path(struct nameidata *nd)

{

	struct dentry *dentry = nd->path.dentry;

	int status;

	struct dentry *dentry = path->dentry;



	/*

	 * only check on filesystems where it's possible for the dentry to

	 * become stale.

	 */

	if (!need_reval_dot(dentry))

	if (likely(!(nd->flags & LOOKUP_JUMPED)))

		return 0;



	if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))

		return 0;



	if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))

		return 0;



	/* Note: we do not d_invalidate() */

	status = d_revalidate(dentry, nd);

	if (status > 0)

		return 0;



	if (!status) {

		d_invalidate(dentry);

	if (!status)

		status = -ESTALE;

	}



	return status;

}
@@ -728,6 +718,7 @@ static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *l 
		path_put(&nd->path);

		nd->path = nd->root;

		path_get(&nd->root);

		nd->flags |= LOOKUP_JUMPED;

	}

	nd->inode = nd->path.dentry->d_inode;
@@ -779,11 +770,8 @@ __do_follow_link(const struct path *link, struct nameidata *nd, void **p) 
		error = 0;

		if (s)

			error = __vfs_follow_link(nd, s);

		else if (nd->last_type == LAST_BIND) {

			error = force_reval_path(&nd->path, nd);

			if (error)

				path_put(&nd->path);

		}

		else if (nd->last_type == LAST_BIND)

			nd->flags |= LOOKUP_JUMPED;

	}

	return error;

}
@@ -1351,7 +1339,7 @@ static int link_path_walk(const char *name, struct nameidata *nd) 
	while (*name=='/')

		name++;

	if (!*name)

		goto return_reval;

		goto return_base;



	if (nd->depth)

		lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
@@ -1385,12 +1373,16 @@ static int link_path_walk(const char *name, struct nameidata *nd) 
		type = LAST_NORM;

		if (this.name[0] == '.') switch (this.len) {

			case 2:

				if (this.name[1] == '.')

				if (this.name[1] == '.') {

					type = LAST_DOTDOT;

					nd->flags |= LOOKUP_JUMPED;

				}

				break;

			case 1:

				type = LAST_DOT;

		}

		if (likely(type == LAST_NORM))

			nd->flags &= ~LOOKUP_JUMPED;



		/* remove trailing slashes? */

		if (!c)
@@ -1456,7 +1448,7 @@ static int link_path_walk(const char *name, struct nameidata *nd) 
				} else

					follow_dotdot(nd);

			}

			goto return_reval;

			goto return_base;

		}

		err = do_lookup(nd, &this, &next, &inode);

		if (err)
@@ -1483,24 +1475,6 @@ static int link_path_walk(const char *name, struct nameidata *nd) 
lookup_parent:

		nd->last = this;

		nd->last_type = type;

		if (type == LAST_NORM)

			goto return_base;

return_reval:

		/*

		 * We bypassed the ordinary revalidation routines.

		 * We may need to check the cached dentry for staleness.

		 */

		if (need_reval_dot(nd->path.dentry)) {

			if (nameidata_drop_rcu_last_maybe(nd))

				return -ECHILD;

			/* Note: we do not d_invalidate() */

			err = d_revalidate(nd->path.dentry, nd);

			if (!err)

				err = -ESTALE;

			if (err < 0)

				break;

			return 0;

		}

return_base:

		if (nameidata_drop_rcu_last_maybe(nd))

			return -ECHILD;
@@ -1523,7 +1497,7 @@ static int path_init(int dfd, const char *name, unsigned int flags, struct namei 
	struct file *file;



	nd->last_type = LAST_ROOT; /* if there are only slashes... */

	nd->flags = flags;

	nd->flags = flags | LOOKUP_JUMPED;

	nd->depth = 0;

	nd->root.mnt = NULL;

	nd->file = NULL;
@@ -1630,6 +1604,9 @@ static int path_lookupat(int dfd, const char *name, 
		br_read_unlock(vfsmount_lock);

	}



	if (!retval)

		retval = handle_reval_path(nd);



	if (nd->file) {

		fput(nd->file);

		nd->file = NULL;
@@ -1690,7 +1667,7 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, 


	/* same as do_path_lookup */

	nd->last_type = LAST_ROOT;

	nd->flags = flags;

	nd->flags = flags | LOOKUP_JUMPED;

	nd->depth = 0;



	nd->path.dentry = dentry;
@@ -1703,6 +1680,8 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, 
	current->total_link_count = 0;



	result = link_path_walk(name, nd);

	if (!result)

		result = handle_reval_path(nd);

	if (result == -ESTALE) {

		/* nd->path had been dropped */

		current->total_link_count = 0;
@@ -1710,8 +1689,11 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, 
		nd->path.mnt = mnt;

		nd->inode = dentry->d_inode;

		path_get(&nd->path);

		nd->flags |= LOOKUP_REVAL;

		nd->flags = flags | LOOKUP_JUMPED | LOOKUP_REVAL;



		result = link_path_walk(name, nd);

		if (!result)

			result = handle_reval_path(nd);

	}

	if (unlikely(!result && !audit_dummy_context() && nd->path.dentry &&

				nd->inode))
@@ -2198,30 +2180,29 @@ static struct file *do_last(struct nameidata *nd, struct path *path, 
{

	struct dentry *dir = nd->path.dentry;

	struct file *filp;

	int error = -EISDIR;

	int error;



	switch (nd->last_type) {

	case LAST_DOTDOT:

		follow_dotdot(nd);

		dir = nd->path.dentry;

	case LAST_DOT:

		if (need_reval_dot(dir)) {

			int status = d_revalidate(nd->path.dentry, nd);

			if (!status)

				status = -ESTALE;

			if (status < 0) {

				error = status;

				goto exit;

			}

		}

		/* fallthrough */

	case LAST_ROOT:

		error = handle_reval_path(nd);

		if (error)

			goto exit;

		error = -EISDIR;

		goto exit;

	case LAST_BIND:

		error = handle_reval_path(nd);

		if (error)

			goto exit;

		audit_inode(pathname, dir);

		goto ok;

	}



	error = -EISDIR;

	/* trailing slashes? */

	if (nd->last.name[nd->last.len])

		goto exit;
@@ -2422,7 +2403,7 @@ struct file *do_filp_open(int dfd, const char *pathname, 
	/*

	 * We have the parent and last component.

	 */

	nd.flags = flags;

	nd.flags = (nd.flags & ~LOOKUP_PARENT) | flags;

	filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);

	while (unlikely(!filp)) { /* trailing symlink */

		struct path link = path;

include/linux/namei.h

+2 −0
Original line number Diff line number Diff line
@@ -63,6 +63,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND}; 
#define LOOKUP_EXCL		0x0400

#define LOOKUP_RENAME_TARGET	0x0800



#define LOOKUP_JUMPED		0x1000



extern int user_path_at(int, const char __user *, unsigned, struct path *);



#define user_path(name, path) user_path_at(AT_FDCWD, name, LOOKUP_FOLLOW, path)