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Commit beb899c4 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Greg Kroah-Hartman
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x86/vsyscall/64: Explicitly set _PAGE_USER in the pagetable hierarchy 



commit 49275fef986abfb8b476e4708aaecc07e7d3e087 upstream.

The kernel is very erratic as to which pagetables have _PAGE_USER set.  The
vsyscall page gets lucky: it seems that all of the relevant pagetables are
among the apparently arbitrary ones that set _PAGE_USER.  Rather than
relying on chance, just explicitly set _PAGE_USER.

This will let us clean up pagetable setup to stop setting _PAGE_USER.  The
added code can also be reused by pagetable isolation to manage the
_PAGE_USER bit in the usermode tables.

[ tglx: Folded paravirt fix from Juergen Gross ]

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7b45ad6e

arch/x86/entry/vsyscall/vsyscall_64.c

+33 −1
Original line number Diff line number Diff line
@@ -37,6 +37,7 @@ 
#include <asm/unistd.h>

#include <asm/fixmap.h>

#include <asm/traps.h>

#include <asm/paravirt.h>



#define CREATE_TRACE_POINTS

#include "vsyscall_trace.h"
@@ -329,16 +330,47 @@ int in_gate_area_no_mm(unsigned long addr) 
	return vsyscall_mode != NONE && (addr & PAGE_MASK) == VSYSCALL_ADDR;

}



/*

 * The VSYSCALL page is the only user-accessible page in the kernel address

 * range.  Normally, the kernel page tables can have _PAGE_USER clear, but

 * the tables covering VSYSCALL_ADDR need _PAGE_USER set if vsyscalls

 * are enabled.

 *

 * Some day we may create a "minimal" vsyscall mode in which we emulate

 * vsyscalls but leave the page not present.  If so, we skip calling

 * this.

 */

static void __init set_vsyscall_pgtable_user_bits(void)

{

	pgd_t *pgd;

	p4d_t *p4d;

	pud_t *pud;

	pmd_t *pmd;



	pgd = pgd_offset_k(VSYSCALL_ADDR);

	set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER));

	p4d = p4d_offset(pgd, VSYSCALL_ADDR);

#if CONFIG_PGTABLE_LEVELS >= 5

	p4d->p4d |= _PAGE_USER;

#endif

	pud = pud_offset(p4d, VSYSCALL_ADDR);

	set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER));

	pmd = pmd_offset(pud, VSYSCALL_ADDR);

	set_pmd(pmd, __pmd(pmd_val(*pmd) | _PAGE_USER));

}



void __init map_vsyscall(void)

{

	extern char __vsyscall_page;

	unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);



	if (vsyscall_mode != NONE)

	if (vsyscall_mode != NONE) {

		__set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall,

			     vsyscall_mode == NATIVE

			     ? PAGE_KERNEL_VSYSCALL

			     : PAGE_KERNEL_VVAR);

		set_vsyscall_pgtable_user_bits();

	}



	BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) !=

		     (unsigned long)VSYSCALL_ADDR);