linux-kernel - [PATCH] x86/ldt: Fix support_pte_mask filtering in map_ldt

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Date:   Mon, 16 Apr 2018 11:43:57 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>
Cc:     hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...e.de>, linux-kernel@...r.kernel.org,
        Joerg Roedel <jroedel@...e.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: [PATCH] x86/ldt: Fix support_pte_mask filtering in map_ldt_struct()

From: Joerg Roedel <jroedel@...e.de>

The |= operator will let us end up with an invalid PTE. Use
the correct &= instead.

Fixes: fb43d6cb91ef ('x86/mm: Do not auto-massage page protections')
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/kernel/ldt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index d41d896481b8..c9b14020f4dd 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -166,7 +166,7 @@ map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot)
 		 */
 		pte_prot = __pgprot(__PAGE_KERNEL_RO & ~_PAGE_GLOBAL);
 		/* Filter out unsuppored __PAGE_KERNEL* bits: */
-		pgprot_val(pte_prot) |= __supported_pte_mask;
+		pgprot_val(pte_prot) &= __supported_pte_mask;
 		pte = pfn_pte(pfn, pte_prot);
 		set_pte_at(mm, va, ptep, pte);
 		pte_unmap_unlock(ptep, ptl);
-- 
2.13.6