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

[Arvin Moezzi]

> >>+
> >>+   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'

I think that's not true. 'count' is changing through the iteration.
The difference in the mem_read():

* while (count > 0) {
* int this_len, retval;
*
*  this_len = (count > PAGE_SIZE) ? PAGE_SIZE : count;
*  retval = access_process_vm(task, src, page, this_len, 0);
*
*  ...
* }

is the fact, that this_len = min(PAGE_SIZE, count) is in the
iteration block, hence retval <= this_len <= count in each iteration
step. So this is ok. But IMHO in your code 'retval' may be bigger than
'count' in the last iteration of the block, because 'max_len' is fix
through your iteration but 'count' is changing. Or am i missing
something?

> James Pearson

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

[Arvin Moezzi]

 +
 +   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'

I think that's not true. 'count' is changing through the iteration.
The difference in the mem_read():

* while (count  0) {
* int this_len, retval;
*
*  this_len = (count  PAGE_SIZE) ? PAGE_SIZE : count;
*  retval = access_process_vm(task, src, page, this_len, 0);
*
*  ...
* }

is the fact, that this_len = min(PAGE_SIZE, count) is in the
iteration block, hence retval = this_len = count in each iteration
step. So this is ok. But IMHO in your code 'retval' may be bigger than
'count' in the last iteration of the block, because 'max_len' is fix
through your iteration but 'count' is changing. Or am i missing
something?

 James Pearson

Arvin
-
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the body of a message to [EMAIL PROTECTED]
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Re: [PATCH -mm] Don't truncate /proc/PID/environ at 4096 characters

[Arvin Moezzi]

2007/9/19, James Pearson <[EMAIL PROTECTED]>:
> +   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?

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

[Arvin Moezzi]

2007/9/19, James Pearson [EMAIL PROTECTED]:
 +   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?

Arvin
-
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