From 61a6bd83abf2f14b2a917b6a0279c88d299267af Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Fri, 14 Sep 2018 12:59:14 +0200 Subject: Revert "x86/mm/legacy: Populate the user page-table with user pgd's" This reverts commit 1f40a46cf47c12d93a5ad9dccd82bd36ff8f956a. It turned out that this patch is not sufficient to enable PTI on 32 bit systems with legacy 2-level page-tables. In this paging mode the huge-page PTEs are in the top-level page-table directory, where also the mirroring to the user-space page-table happens. So every huge PTE exits twice, in the kernel and in the user page-table. That means that accessed/dirty bits need to be fetched from two PTEs in this mode to be safe, but this is not trivial to implement because it needs changes to generic code just for the sake of enabling PTI with 32-bit legacy paging. As all systems that need PTI should support PAE anyway, remove support for PTI when 32-bit legacy paging is used. Fixes: 7757d607c6b3 ('x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32') Reported-by: Meelis Roos Signed-off-by: Joerg Roedel Signed-off-by: Thomas Gleixner Cc: hpa@zytor.com Cc: linux-mm@kvack.org Cc: Linus Torvalds Cc: Andy Lutomirski Cc: Dave Hansen Cc: Borislav Petkov Cc: Andrea Arcangeli Link: https://lkml.kernel.org/r/1536922754-31379-1-git-send-email-joro@8bytes.org --- security/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'security') diff --git a/security/Kconfig b/security/Kconfig index 27d8b2688f75..d9aa521b5206 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -57,7 +57,7 @@ config SECURITY_NETWORK config PAGE_TABLE_ISOLATION bool "Remove the kernel mapping in user mode" default y - depends on X86 && !UML + depends on (X86_64 || X86_PAE) && !UML help This feature reduces the number of hardware side channels by ensuring that the majority of kernel addresses are not mapped -- cgit v1.2.3