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Diffstat (limited to 'fs/exportfs/expfs.c')
-rw-r--r--fs/exportfs/expfs.c136
1 files changed, 130 insertions, 6 deletions
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 813011aad700..99294a23cd54 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -514,17 +514,141 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
int (*acceptable)(void *, struct dentry *), void *context)
{
struct export_operations *nop = mnt->mnt_sb->s_export_op;
- struct dentry *result;
+ struct dentry *result, *alias;
+ int err;
- if (nop->decode_fh) {
- result = nop->decode_fh(mnt->mnt_sb, fid->raw, fh_len,
+ /*
+ * Old way of doing things. Will go away soon.
+ */
+ if (!nop->fh_to_dentry) {
+ if (nop->decode_fh) {
+ return nop->decode_fh(mnt->mnt_sb, fid->raw, fh_len,
fileid_type, acceptable, context);
+ } else {
+ return export_decode_fh(mnt->mnt_sb, fid->raw, fh_len,
+ fileid_type, acceptable, context);
+ }
+ }
+
+ /*
+ * Try to get any dentry for the given file handle from the filesystem.
+ */
+ result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
+ if (!result)
+ result = ERR_PTR(-ESTALE);
+ if (IS_ERR(result))
+ return result;
+
+ if (S_ISDIR(result->d_inode->i_mode)) {
+ /*
+ * This request is for a directory.
+ *
+ * On the positive side there is only one dentry for each
+ * directory inode. On the negative side this implies that we
+ * to ensure our dentry is connected all the way up to the
+ * filesystem root.
+ */
+ if (result->d_flags & DCACHE_DISCONNECTED) {
+ err = reconnect_path(mnt->mnt_sb, result);
+ if (err)
+ goto err_result;
+ }
+
+ if (!acceptable(context, result)) {
+ err = -EACCES;
+ goto err_result;
+ }
+
+ return result;
} else {
- result = export_decode_fh(mnt->mnt_sb, fid->raw, fh_len,
- fileid_type, acceptable, context);
+ /*
+ * It's not a directory. Life is a little more complicated.
+ */
+ struct dentry *target_dir, *nresult;
+ char nbuf[NAME_MAX+1];
+
+ /*
+ * See if either the dentry we just got from the filesystem
+ * or any alias for it is acceptable. This is always true
+ * if this filesystem is exported without the subtreecheck
+ * option. If the filesystem is exported with the subtree
+ * check option there's a fair chance we need to look at
+ * the parent directory in the file handle and make sure
+ * it's connected to the filesystem root.
+ */
+ alias = find_acceptable_alias(result, acceptable, context);
+ if (alias)
+ return alias;
+
+ /*
+ * Try to extract a dentry for the parent directory from the
+ * file handle. If this fails we'll have to give up.
+ */
+ err = -ESTALE;
+ if (!nop->fh_to_parent)
+ goto err_result;
+
+ target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
+ fh_len, fileid_type);
+ if (!target_dir)
+ goto err_result;
+ err = PTR_ERR(target_dir);
+ if (IS_ERR(target_dir))
+ goto err_result;
+
+ /*
+ * And as usual we need to make sure the parent directory is
+ * connected to the filesystem root. The VFS really doesn't
+ * like disconnected directories..
+ */
+ err = reconnect_path(mnt->mnt_sb, target_dir);
+ if (err) {
+ dput(target_dir);
+ goto err_result;
+ }
+
+ /*
+ * Now that we've got both a well-connected parent and a
+ * dentry for the inode we're after, make sure that our
+ * inode is actually connected to the parent.
+ */
+ err = exportfs_get_name(target_dir, nbuf, result);
+ if (!err) {
+ mutex_lock(&target_dir->d_inode->i_mutex);
+ nresult = lookup_one_len(nbuf, target_dir,
+ strlen(nbuf));
+ mutex_unlock(&target_dir->d_inode->i_mutex);
+ if (!IS_ERR(nresult)) {
+ if (nresult->d_inode) {
+ dput(result);
+ result = nresult;
+ } else
+ dput(nresult);
+ }
+ }
+
+ /*
+ * At this point we are done with the parent, but it's pinned
+ * by the child dentry anyway.
+ */
+ dput(target_dir);
+
+ /*
+ * And finally make sure the dentry is actually acceptable
+ * to NFSD.
+ */
+ alias = find_acceptable_alias(result, acceptable, context);
+ if (!alias) {
+ err = -EACCES;
+ goto err_result;
+ }
+
+ return alias;
}
- return result;
+ err_result:
+ dput(result);
+ return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(exportfs_decode_fh);