Re: [Libevent-users] [PATCH] evbuffer_search_range fails when searching the last byte

["Andrew W. Nosenko" <andrew.w.nosenko@xxxxxxxxx>]

On Tue, Jun 7, 2011 at 16:30, Nir Soffer <nirsof@xxxxxxxxx> wrote:
>
> On Jun 7, 2011, at 4:03 AM, Nick Mathewson wrote:
>
>> On Mon, Jun 6, 2011 at 8:37 PM, Nir Soffer <nirsof@xxxxxxxxx> wrote:
>> Here's another patch that might make stuff work.  Before I'd apply it,
>> I'd like to have a look through everything that's using
>> evbuffer_ptr_set() and evbuffer_ptr right now to make sure that
>> nothing will freak out if it gets a pointer like this.
>>
>> What do you think?
>
> Here is a new test case that fail with this patch:
>
>    /* Search the next 18 bytes for "attack" */
>    tt_int_op(evbuffer_ptr_set(buf, &end, 18, EVBUFFER_PTR_SET), ==, 0);
>    pos = evbuffer_search_range(buf, "attack", 6, NULL, &end);
>    tt_int_op(pos.pos, ==, 11);
>
> The use case is simple - I want to limit the search to some range, which
> happen to be longer then the buffer. To make this work with this patch, I
> have to do something like this:
>
>        size_t length = evbuffer_get_length(buf);
>
>        if (limit > length)
>                limit = length;
>
>        evbuffer_ptr_set(buf, &end, limit, EVBUFFER_PTR_SET);
>        pos = evbuffer_search_range(buf, "needle", 6, NULL, &end);
>
> But what I would like to do is this:
>
>        evbuffer_ptr_set(buf, &end, limit, EVBUFFER_PTR_SET);
>        pos = evbuffer_search_range(buf, "needle", 6, NULL, &end);
>
> So evebuffer_ptr_set should succeed even if position is after the end of the
> buffer;
>
> The attached patch make it work, but accepting any position, even if it out
> of the buffer range.
>
> I did not inspect the code handling these ranges yet - it is possible that
> such ranges will lead to accessing memory you should not access, if the code
> was depending on ranges to be always within the buffer.

How these changes expected to affect evbuffer_read(), evbuffer_write()
and like functions?

-- 
Andrew W. Nosenko <andrew.w.nosenko@xxxxxxxxx>
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