linux-kernel - [tip:x86/pti] x86/vsyscall/64: Use proper accessor to update p4d entry

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Date:   Tue, 20 Mar 2018 01:09:51 -0700
From:   tip-bot for Boris Ostrovsky <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, jgross@...e.com, mingo@...nel.org,
        tglx@...utronix.de, boris.ostrovsky@...cle.com, luto@...nel.org,
        hpa@...or.com
Subject: [tip:x86/pti] x86/vsyscall/64: Use proper accessor to update p4d
 entry

Commit-ID:  f9ee6990bd505ecefa014f5e699b3c4d25860d80
Gitweb:     https://git.kernel.org/tip/f9ee6990bd505ecefa014f5e699b3c4d25860d80
Author:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
AuthorDate: Mon, 19 Mar 2018 10:31:54 -0400
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 20 Mar 2018 09:04:51 +0100

x86/vsyscall/64: Use proper accessor to update p4d entry

Writing to it directly does not work for Xen PV guests.

Fixes: 49275fef986a ("x86/vsyscall/64: Explicitly set _PAGE_USER in the pagetable hierarchy")
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Juergen Gross <jgross@...e.com>
Acked-by: Andy Lutomirski <luto@...nel.org>
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/20180319143154.3742-1-boris.ostrovsky@oracle.com

---
 arch/x86/entry/vsyscall/vsyscall_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 8560ef68a9d6..317be365bce3 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -347,7 +347,7 @@ void __init set_vsyscall_pgtable_user_bits(pgd_t *root)
 	set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER));
 	p4d = p4d_offset(pgd, VSYSCALL_ADDR);
 #if CONFIG_PGTABLE_LEVELS >= 5
-	p4d->p4d |= _PAGE_USER;
+	set_p4d(p4d, __p4d(p4d_val(*p4d) | _PAGE_USER));
 #endif
 	pud = pud_offset(p4d, VSYSCALL_ADDR);
 	set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER));