linux-kernel - [PATCH 1/3] x86: Honour passed pgprot in track_pfn_insert() and track_pfn

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Date:	Mon, 25 Jan 2016 12:25:15 -0500
From:	Matthew Wilcox <matthew.r.wilcox@...el.com>
To:	Ingo Molnar <mingo@...hat.com>,
	Andy Lutomirski <luto@...capital.net>
Cc:	Matthew Wilcox <willy@...ux.intel.com>,
	Kees Cook <keescook@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 1/3] x86: Honour passed pgprot in track_pfn_insert() and track_pfn_remap()

From: Matthew Wilcox <willy@...ux.intel.com>

track_pfn_insert() overwrites the pgprot that is passed in with a value
based on the VMA's page_prot.  This is a problem for people trying to
do clever things with the new vm_insert_pfn_prot() as it will simply
overwrite the passed protection flags.  If we use the current value of
the pgprot as the base, then it will behave as people are expecting.

Also fix track_pfn_remap() in the same way.

Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>
---
 arch/x86/mm/pat.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index f4ae536..04e2e71 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -943,7 +943,7 @@ int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
 			return -EINVAL;
 	}
 
-	*prot = __pgprot((pgprot_val(vma->vm_page_prot) & (~_PAGE_CACHE_MASK)) |
+	*prot = __pgprot((pgprot_val(*prot) & (~_PAGE_CACHE_MASK)) |
 			 cachemode2protval(pcm));
 
 	return 0;
@@ -959,7 +959,7 @@ int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
 
 	/* Set prot based on lookup */
 	pcm = lookup_memtype(pfn_t_to_phys(pfn));
-	*prot = __pgprot((pgprot_val(vma->vm_page_prot) & (~_PAGE_CACHE_MASK)) |
+	*prot = __pgprot((pgprot_val(*prot) & (~_PAGE_CACHE_MASK)) |
 			 cachemode2protval(pcm));
 
 	return 0;
-- 
2.7.0.rc3