On Mon, May 09, 2022 at 08:37:42PM -0700, Andrew Morton wrote: > On Mon, 10 Jan 2022 23:15:27 +0000 "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> wrote: > > > If you are copying to an address in the kmap region, you may not copy > > across a page boundary, > > In the source, the destination or in both, and why may we not? This depends on direction. For copying to userspace, the source (kmap). For copying from userspace, the destination (kmap). > > no matter what the size of the underlying > > allocation. You can't kmap() a slab page because slab pages always > > come from low memory. As in it'll be processed as a slab page instead of kmap by the usercopy checks? -- Kees Cook
