linux-kernel - Re: [patch] hfs: fix hfs

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Date:	Tue, 26 Jan 2016 13:54:06 -0800
From:	Viacheslav Dubeyko <slava@...eyko.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
Cc:	Chengyu Song <csong84@...ech.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] hfs: fix hfs_readdir()

On Tue, 2016-01-26 at 22:18 +0300, Dan Carpenter wrote:
> Hm, I completely didn't see that it was a union instead of a struct.  I
> still think my fix is actually correct though.  Now that you point out
> the union, I see that my change is equivalent to just removing the '&'
> char.
> 
> -	memcpy(&rd->key, &fd.key, sizeof(struct hfs_cat_key));
> +	memcpy(&rd->key, fd.key, sizeof(struct hfs_cat_key));
> 

Yeahh, it looks correct right now. The rd is the pointer that includes
struct hfs_cat_key object. So, we need to use &rd->key. But on another
side we have struct hfs_find_data object on the stack. And this object
includes the pointer on union btree_key. We want to copy struct
hfs_cat_key object and we should use sizeof(struct hfs_cat_key).

> We don't want to copy sizeof(*fd.key) because that would write past the
> end of the destination struct.
> 
> On Tue, Jan 26, 2016 at 10:18:56AM -0800, Viacheslav Dubeyko wrote:
> > Another worry could be the "search_key" field of the struct
> > hfs_find_data.
> 
> I don't understand what you mean here.
> 

I mean here that we could have another incorrect copy operations for
"search_key" field. That's all.

Thanks,
Vyacheslav Dubeyko.