On Mon, Dec 4, 2017 at 6:08 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > > The KERNEL_PAGE_TABLE_ISOLATION code attempts to "poison" the user > portion of the kernel page tables. It detects entries that it wants that it > wants to poison in two ways: > > * Looking for addresses >= PAGE_OFFSET > > * Looking for entries without _PAGE_USER set > > But, to allow the _PAGE_USER check to work, it must never be set on > init_mm entries, and an earlier patch in this series ensured that it > will never be set. > > The VDSO is at a address >= PAGE_OFFSET and it is also mapped by init_mm. > Because of the earlier, KERNEL_PAGE_TABLE_ISOLATION-enforced restriction, > _PAGE_USER is never set which makes the VDSO unreadable to userspace. > > This makes the "NATIVE" case totally unusable since userspace can not even > see the memory any more. Disable it whenever KERNEL_PAGE_TABLE_ISOLATION > is enabled. > > Also add some help text about how KERNEL_PAGE_TABLE_ISOLATION might > affect the emulation case as well. > I think my other suggestion may obsolete this patch. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
