Re: [PATCH v2 7/11] Uprobes Implementation

[Linus Torvalds]

On Thu, 13 May 2010, Oleg Nesterov wrote:
> 
> But I still think this doesn't actually matter, replace_page() shouldn't
> preserve the mapping, it should always install the anonymous page. I can
> be wrong, of course.

Well, if I reasd the patches right, uprobes will use "copy_to_user()" for 
the self-probing case. So that would definitely just modify a shared 
mapping.

Of course, arguably, who really cares? As long as it's not a security 
issue (and it isn't - since the person could just have written to the 
thing directly instead), I guess it doesn't much matter. But it's a bit 
sad when a probing feature either

 - changes a global mapping that may be executed by other non-related 
   processes that the prober isn't even _aware_ of.

 - changes semantics by creating a non-coherent private page

so arguably it would be good to just make the rule be that you cannot 
probe a shared mapping. Because whatever you do, it's always the wrong 
thing.

			Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/