[tip:x86/pti] x86/mm/pti: Keep permissions when cloning kernel text in pti_clone_kernel_text()

[tip-bot for Joerg Roedel]

Commit-ID:  1ac228a7c87f697d1d01eb6362a6b5246705b0dd
Gitweb:     https://git.kernel.org/tip/1ac228a7c87f697d1d01eb6362a6b5246705b0dd
Author:     Joerg Roedel <jroedel@xxxxxxx>
AuthorDate: Wed, 18 Jul 2018 11:41:05 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Fri, 20 Jul 2018 01:11:45 +0200

x86/mm/pti: Keep permissions when cloning kernel text in pti_clone_kernel_text()

Mapping the kernel text area to user-space makes only sense if it has the
same permissions as in the kernel page-table.  If permissions are different
this will cause a TLB reload when using the kernel page-table, which is as
good as not mapping it at all.

On 64-bit kernels this patch makes no difference, as the whole range cloned
by pti_clone_kernel_text() is mapped RO anyway. On 32 bit there are
writeable mappings in the range, so just keep the permissions as they are.

Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Pavel Machek <pavel@xxxxxx>
Cc: "H . Peter Anvin" <hpa@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Jiri Kosina <jkosina@xxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Eduardo Valentin <eduval@xxxxxxxxxx>
Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: aliguori@xxxxxxxxxx
Cc: daniel.gruss@xxxxxxxxxxxxxx
Cc: hughd@xxxxxxxxxx
Cc: keescook@xxxxxxxxxx
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Waiman Long <llong@xxxxxxxxxx>
Cc: "David H . Gutteridge" <dhgutteridge@xxxxxxxxxxxx>
Cc: joro@xxxxxxxxxx
Link: https://lkml.kernel.org/r/1531906876-13451-29-git-send-email-joro@xxxxxxxxxx

---
 arch/x86/mm/pti.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 453d23760941..e41ee93c430d 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -482,7 +482,7 @@ void pti_clone_kernel_text(void)
 	 * pti_set_kernel_image_nonglobal() did to clear the
 	 * global bit.
 	 */
-	pti_clone_pmds(start, end, _PAGE_RW);
+	pti_clone_pmds(start, end, 0);
 }
 
 /*