Commit acff81ec authored Dec 04, 2015 by Miklos Szeredi Committed by Al Viro Dec 06, 2015

ovl: fix permission checking for setattr



[Al Viro] The bug is in being too enthusiastic about optimizing ->setattr()
away - instead of "copy verbatim with metadata" + "chmod/chown/utimes"
(with the former being always safe and the latter failing in case of
insufficient permissions) it tries to combine these two.  Note that copyup
itself will have to do ->setattr() anyway; _that_ is where the elevated
capabilities are right.  Having these two ->setattr() (one to set verbatim
copy of metadata, another to do what overlayfs ->setattr() had been asked
to do in the first place) combined is where it breaks.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

parent 31ade3b8

fs/overlayfs/inode.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -49,13 +49,13 @@ int ovl_setattr(struct dentry dentry, struct iattr attr)
		if (err)
		goto out;

		err = ovl_copy_up(dentry);
		if (!err) {
		upperdentry = ovl_dentry_upper(dentry);
		if (upperdentry) {

		mutex_lock(&upperdentry->d_inode->i_mutex);
		err = notify_change(upperdentry, attr, NULL);
		mutex_unlock(&upperdentry->d_inode->i_mutex);
		} else {
		err = ovl_copy_up_last(dentry, attr, false);
		}
		ovl_drop_write(dentry);
		out: