btrfs: hold a ref on the root in btrfs_search_path_in_tree_user

We can wander into a different root, so grab a ref on the root we look
up.  Later on we make root = fs_info->tree_root so we need this separate
out label to make sure we do the right cleanup only in the case we're
looking up a different root.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 9c8a9944f848a5e0a9c7dbbc66e822c7bd9c6e77..7e1af2d46dd2dacec031af0f50c5669ea543f8c2 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2401,7 +2401,7 @@ static int btrfs_search_path_in_tree_user(struct inode *inode,
        unsigned long item_len;
        struct btrfs_inode_ref *iref;
        struct btrfs_root_ref *rref;
-       struct btrfs_root *root;
+       struct btrfs_root *root = NULL;
        struct btrfs_path *path;
        struct btrfs_key key, key2;
        struct extent_buffer *leaf;
@@ -2431,6 +2431,10 @@ static int btrfs_search_path_in_tree_user(struct inode *inode,
                        ret = PTR_ERR(root);
                        goto out;
                }
+               if (!btrfs_grab_fs_root(root)) {
+                       ret = -ENOENT;
+                       goto out;
+               }
 
                key.objectid = dirid;
                key.type = BTRFS_INODE_REF_KEY;
@@ -2438,15 +2442,15 @@ static int btrfs_search_path_in_tree_user(struct inode *inode,
                while (1) {
                        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                        if (ret < 0) {
-                               goto out;
+                               goto out_put;
                        } else if (ret > 0) {
                                ret = btrfs_previous_item(root, path, dirid,
                                                          BTRFS_INODE_REF_KEY);
                                if (ret < 0) {
-                                       goto out;
+                                       goto out_put;
                                } else if (ret > 0) {
                                        ret = -ENOENT;
-                                       goto out;
+                                       goto out_put;
                                }
                        }
 
@@ -2460,7 +2464,7 @@ static int btrfs_search_path_in_tree_user(struct inode *inode,
                        total_len += len + 1;
                        if (ptr < args->path) {
                                ret = -ENAMETOOLONG;
-                               goto out;
+                               goto out_put;
                        }
 
                        *(ptr + len) = '/';
@@ -2471,10 +2475,10 @@ static int btrfs_search_path_in_tree_user(struct inode *inode,
                        ret = btrfs_previous_item(root, path, dirid,
                                                  BTRFS_INODE_ITEM_KEY);
                        if (ret < 0) {
-                               goto out;
+                               goto out_put;
                        } else if (ret > 0) {
                                ret = -ENOENT;
-                               goto out;
+                               goto out_put;
                        }
 
                        leaf = path->nodes[0];
@@ -2482,26 +2486,26 @@ static int btrfs_search_path_in_tree_user(struct inode *inode,
                        btrfs_item_key_to_cpu(leaf, &key2, slot);
                        if (key2.objectid != dirid) {
                                ret = -ENOENT;
-                               goto out;
+                               goto out_put;
                        }
 
                        temp_inode = btrfs_iget(sb, &key2, root);
                        if (IS_ERR(temp_inode)) {
                                ret = PTR_ERR(temp_inode);
-                               goto out;
+                               goto out_put;
                        }
                        ret = inode_permission(temp_inode, MAY_READ | MAY_EXEC);
                        iput(temp_inode);
                        if (ret) {
                                ret = -EACCES;
-                               goto out;
+                               goto out_put;
                        }
 
                        if (key.offset == upper_limit.objectid)
                                break;
                        if (key.objectid == BTRFS_FIRST_FREE_OBJECTID) {
                                ret = -EACCES;
-                               goto out;
+                               goto out_put;
                        }
 
                        btrfs_release_path(path);
@@ -2512,15 +2516,16 @@ static int btrfs_search_path_in_tree_user(struct inode *inode,
 
                memmove(args->path, ptr, total_len);
                args->path[total_len] = '\0';
+               btrfs_put_fs_root(root);
+               root = NULL;
                btrfs_release_path(path);
        }
 
        /* Get the bottom subvolume's name from ROOT_REF */
-       root = fs_info->tree_root;
        key.objectid = treeid;
        key.type = BTRFS_ROOT_REF_KEY;
        key.offset = args->treeid;
-       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+       ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
        if (ret < 0) {
                goto out;
        } else if (ret > 0) {
@@ -2547,6 +2552,8 @@ static int btrfs_search_path_in_tree_user(struct inode *inode,
        read_extent_buffer(leaf, args->name, item_off, item_len);
        args->name[item_len] = 0;
 
+out_put:
+       btrfs_put_fs_root(root);
 out:
        btrfs_free_path(path);
        return ret;