Re: [RFC][PATCHSET] iov_iter work

[Christoph Hellwig]

On Mon, Jun 07, 2021 at 02:43:40PM +0000, Al Viro wrote:
> > It can't even happen for the legacy architectures, given that the
> > remaining set_fs() areas are small and never do iov_iter based I/O.
> 
> 	Umm...  It's a bit trickier than that - e.g. a kernel thread on
> a CONFIG_SET_FS target passing a kernel pointer to vfs_read() could've
> ended up with new_sync_write() hitting iov_iter_init().

Yes, that is a possbility, but rather unlikely - it would require an
arch-specific thread using iov_iter_init.  iov_iter_init instances are
rather fewer, and only very few in arch code.

> 	AFAICS, we don't have any instances of that, but it's not
> as simple as "we don't do any iov_iter work under set_fs(KERNEL_DS)"

Indeed.