Re: [PATCH 5/6] nfs: check all iov segments for correct memory access rights

Chuck Lever
2006-05-19T18:46:33Z

Andrew Morton wrote:
> Chuck Lever <cel@netapp.com> wrote:
>> +static ssize_t check_access_ok(int type, const struct iovec *iov, unsigned long nr_segs)
>> +{
>> + ssize_t count = 0;
>> + ssize_t retval = -EINVAL;
>> + unsigned long seg;
>> +
>> + for (seg = 0; seg < nr_segs; seg++) {
>> + void __user *buf = iov[seg].iov_base;
>> + ssize_t len = (ssize_t) iov[seg].iov_len;
>> +
>> + if (len < 0) /* size_t not fitting an ssize_t .. */
>> + goto out;
>
> do_readv_writev() already checked for negative iov_len, and that's the more
> appropriate place to do it, rather than duplicating it in each filesystem
> (or forgetting to!)
>
> So is this check really needed?

Ok, didn't see that function before. Badari, is this checking still needed?

>> + if (unlikely(!access_ok(type, buf, len))) {
>> + retval = -EFAULT;
>> + goto out;
>> + }
>
> Now what's up here? Why does NFS, at this level, care about the page's
> virtual address? get_user_pages() will handle that?

Interesting point. That may be a historical artifact that can be
removed. I'll take a look.

--
corporate: cel at netapp dot com
personal: chucklever at bigfoot dot com