linux-kernel - Re: [PATCH -mm] Don't truncate /proc/PID/environ at 4096 characters

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Message-ID: <46F39319.9090705@moving-picture.com>
Date:	Fri, 21 Sep 2007 10:47:05 +0100
From:	James Pearson <james-p@...ing-picture.com>
To:	Arvin Moezzi <moezzia@...il.com>
CC:	linux-kernel@...r.kernel.org, aarapov@...hat.com,
	akpm@...ux-foundation.org, hpa@...or.com
Subject: Re: [PATCH -mm] Don't truncate /proc/PID/environ at 4096 characters

Arvin Moezzi wrote:
> 2007/9/19, James Pearson <james-p@...ing-picture.com>:
> 
>>+       while (count > 0) {
>>+               int this_len, retval;
>>+
>>+               this_len = mm->env_end - (mm->env_start + src);
>>+
>>+               if (this_len <= 0)
>>+                       break;
>>+
>>+               if (this_len > max_len)
>>+                       this_len = max_len;
>>+
>>+               retval = access_process_vm(task, (mm->env_start + src),
>>+                       page, this_len, 0);
>>+
>>+               if (retval <= 0) {
>>+                       ret = retval;
>>+                       break;
>>+               }
>>+
>>+               if (copy_to_user(buf, page, retval)) {
> 
>                                                                 ^^^^
> shouldn't you only copy min(count,retval) bytes? otherwise you could
> write beyond the users buffer "buf", right?

AFAIK, 'retval' can never be greater than 'this_len', which can never be 
greater than 'max_len', which can never be greater than 'count'

James Pearson
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