Re: [PATCH v4] tee: Use iov_iter to better support shared buffer registration

On 12/4/23 5:42 AM, Sumit Garg wrote:

IMO, access_ok() should be the first thing that import_ubuf() or import_single_range() should do, something as follows:

diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 8ff6824a1005..4aee0371824c 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1384,10 +1384,10 @@ EXPORT_SYMBOL(import_single_range);

int import_ubuf(int rw, void __user *buf, size_t len, struct iov_iter *i) {

•   if (len > MAX_RW_COUNT)
  

•           len = MAX_RW_COUNT;
    if (unlikely(!access_ok(buf, len)))
            return -EFAULT;
  

•   if (len > MAX_RW_COUNT)
  

•           len = MAX_RW_COUNT;
  
    iov_iter_ubuf(i, rw, buf, len);
    return 0;
  
  

Jens A., Al Viro,

Was there any particular reason which I am unaware of to perform access_ok() check on modified input length?

This change makes sense to me, and seems consistent with what is done elsewhere too.