linux-kernel - [PATCH v2 2/3] mm: mprotect: preserve special page protection bits

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Message-Id: <1408831921-10168-3-git-send-email-pfeiner@google.com>
Date:	Sat, 23 Aug 2014 18:12:00 -0400
From:	Peter Feiner <pfeiner@...gle.com>
To:	linux-mm@...ck.org
Cc:	linux-kernel@...r.kernel.org, Peter Feiner <pfeiner@...gle.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Jamie Liu <jamieliu@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v2 2/3] mm: mprotect: preserve special page protection bits

We don't want to zap special page protection bits on mprotect.
Analogous to the bug fixed in c9d0bf241451a3ab7d02e1652c22b80cd7d93e8f
where vm_page_prot bits set by drivers were zapped when write
notifications were enabled on new VMAs.

Signed-off-by: Peter Feiner <pfeiner@...gle.com>
---
 mm/mprotect.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index c43d557..1c1afd4 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -324,7 +324,7 @@ success:
 					  vm_get_page_prot(newflags));
 
 	if (vma_wants_writenotify(vma)) {
-		vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
+		vma_enable_writenotify(vma);
 		dirty_accountable = 1;
 	}
 
-- 
2.1.0.rc2.206.gedb03e5

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