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 <ernesto.mnd.fernandez@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 8d8370ddb6b29655f05ffe2855bd78f9937c7363..1ba49ebe67da39f6daf0a9a6f0ff63fff8554935 100644 (file)
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -114,13 +114,17 @@ out:
 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;
 }
 
 /*