btrfs: preserve i_mode if __btrfs_set_acl() fails

When changing a file's acl mask, btrfs_set_acl() will first set the group bits of i_mode to the value of the mask, and only then set the actual extended attribute representing the new acl. If the second part fails (due to lack of space, for example) and the file had no acl attribute to begin with, the system will from now on assume that the mask permission bits are actual group permission bits, potentially granting access to the wrong users. Prevent this by restoring the original mode bits if __btrfs_set_acl fails. Signed-off-by: Ernesto A. Fernández <[email protected]> Reviewed-by: David Sterba <[email protected]> Signed-off-by: David Sterba <[email protected]>
MaxKrummenacher · Aug 21, 2017 · d7d8249 · d7d8249
1 parent 408fbf1
commit d7d8249
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
@@ -114,13 +114,17 @@ static int __btrfs_set_acl(struct btrfs_trans_handle *trans,
 int btrfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 {
 	int ret;
+	umode_t old_mode = inode->i_mode;
 
 	if (type == ACL_TYPE_ACCESS && acl) {
 		ret = posix_acl_update_mode(inode, &inode->i_mode, &acl);
 		if (ret)
 			return ret;
 	}
-	return __btrfs_set_acl(NULL, inode, acl, type);
+	ret = __btrfs_set_acl(NULL, inode, acl, type);
+	if (ret)
+		inode->i_mode = old_mode;
+	return ret;
 }
 
 /*