btrfs: tree_search, copy_to_sk: return EOVERFLOW for too small buffer

In copy_to_sk, if an item is too large for the given buffer, it now returns
-EOVERFLOW instead of copying a search_header with len = 0. For backward
compatibility for the first item it still copies such a header to the buffer,
but not any other following items, which could have fitted.

tree_search changes -EOVERFLOW back to 0 to behave similiar to the way it
behaved before this patch.

Signed-off-by: Gerhard Heift <Gerhard@Heift.Name>
Signed-off-by: Chris Mason <clm@fb.com>
Acked-by: David Sterba <dsterba@suse.cz>

1 files changed, 26 insertions, 2 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 775640475e35..6e09fc1c1c18 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1990,8 +1990,20 @@ static noinline int copy_to_sk(struct btrfs_root *root,
                 if (!key_in_sk(key, sk))
                         continue;
 
-                if (sizeof(sh) + item_len > buf_size)
+                if (sizeof(sh) + item_len > buf_size) {
+                        if (*num_found) {
+                                ret = 1;
+                                goto out;
+                        }
+
+                        /*
+                         * return one empty item back for v1, which does not
+                         * handle -EOVERFLOW
+                         */
+
                         item_len = 0;
+                        ret = -EOVERFLOW;
+                }
 
                 if (sizeof(sh) + item_len + *sk_offset > buf_size) {
                         ret = 1;
@@ -2017,6 +2029,9 @@ static noinline int copy_to_sk(struct btrfs_root *root,
                 }
                 (*num_found)++;
 
+                if (ret) /* -EOVERFLOW from above */
+                        goto out;
+
                 if (*num_found >= sk->nr_items) {
                         ret = 1;
                         goto out;
@@ -2095,7 +2110,8 @@ static noinline int search_ioctl(struct inode *inode,
                         break;
 
         }
-        ret = 0;
+        if (ret > 0)
+                ret = 0;
 err:
         sk->nr_items = num_found;
         btrfs_free_path(path);
@@ -2118,6 +2134,14 @@ static noinline int btrfs_ioctl_tree_search(struct file *file,
 
         inode = file_inode(file);
         ret = search_ioctl(inode, &args->key, sizeof(args->buf), args->buf);
+
+        /*
+         * In the origin implementation an overflow is handled by returning a
+         * search header with a len of zero, so reset ret.
+         */
+        if (ret == -EOVERFLOW)
+                ret = 0;
+
         if (ret == 0 && copy_to_user(argp, args, sizeof(*args)))
                 ret = -EFAULT;
         kfree(args);