Re: [PATCH net-next] net: devmem: remove min_t(iter_iov_len) in sendmsg

[Al Viro]

On Fri, May 16, 2025 at 06:24:03PM -0700, Stanislav Fomichev wrote:
> On 05/17, Al Viro wrote:
> > On Fri, May 16, 2025 at 05:04:31PM -0700, Stanislav Fomichev wrote:
> > > iter_iov_len looks broken for UBUF. When iov_iter_advance is called
> > > for UBUF, it increments iov_offset and also decrements the count.
> > > This makes the iterator only go over half of the range (unless I'm
> > > missing something).
> > 
> > What do you mean by "broken"?  iov_iter_len(from) == "how much data is
> > left in that iterator".  That goes for all flavours, UBUF included...
> > 
> > Confused...

[snip]

> iov_len. And now, calling iter_iov_len (which does iov_len - iov_offset)

Wait a sec...  Sorry, I've misread that as iov_iter_count(); iter_iov_len()
(as well as iter_iov_addr()) should not be used on anything other that
ITER_IOVEC

<checks>

Wait, in the same commit there's
+       if (iov_iter_type(from) != ITER_IOVEC)
+               return -EFAULT;

shortly prior to the loop iter_iov_{addr,len}() are used.  What am I missing now?