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SubjectRe: [PATCH v6] Added PR_SET_PROCTITLE_AREA option for prctl()

* KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:

> + /*
> + * If argv and environ aren't continuous (i.e. the process used
> + * prctl(PR_SET_PROCTITLE_AREA)), we don't care environ override.

s/dont't care environ override/don't care about the evironment override/

> + case PR_SET_PROCTITLE_AREA: {
> + struct mm_struct *mm = current->mm;
> + unsigned long addr = arg2;
> + unsigned long len = arg3;
> + unsigned long end = arg2 + arg3;

would be cleaner to write the latter as 'addr + len'.

> + if (len > PAGE_SIZE)
> + return -EINVAL;
> +
> + if (addr >= end)
> + return -EINVAL;
> +
> + /*
> + * If the process pass broken pointer, EFAULT is might better
> + * than ps output zero-length proctitle. Plus if
> + * the process pass kernel address (or something-else),
> + * We have to block it. Oherwise, strange exploit
> + * chance is there.
> + */
> + if (!access_ok(VERIFY_READ, addr, len))
> + return -EFAULT;

the addr >= end check looks (partly) duplicative of the access_ok()
check.

> +
> + down_write(&mm->mmap_sem);
> + mm->arg_start = addr;
> + mm->arg_end = end;
> + up_write(&mm->mmap_sem);

well we might as well name 'addr' as 'start' and have a match then here
too.

The feature looks useful, but the choice of a prctl as an API is strange
- it limits us to the current task only - while the ability to set
arguments for another task looks a more generic (and potentially more
useful) solution.

Ingo


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