On Mon, Apr 23, 2018 at 09:45:38AM -0700, Linus Torvalds wrote: > Just one question: have you checked the page table setup for the > basics wrt the USER bit in particular? Just checked that and there are no pages with GLB and USR set, not even a vdso page. > No global pages should be marked PAGE_USER, with the possible > exception of that nasty old vsyscall page. The vsyscall page does not exist on plain 32 bit, no? All I could find there is the vdso page, and that has no compat mapping anymore in recent upstream kernels. To my understanding the vdso page is mapped into the user-space portion of the address space. At least that is what I found while looking at this, but I might have missed something. I actually ran into a vdso issue when porting these changes to 3.0 (where there still is a compat vdso mapping in the fixmap) so I checked my upstream code too, but didn't find the code to setup a vdso in the fixmap. > And it would be nice to verify that the page tables for kernel > mappings also don't have PAGE_USER on them, although again that > vsyscall page can cause problems. Checked that too, all USR mappings are below PAGE_OFFSET. Regards, Joerg
