linux-kernel - [PATCH] x86: strengthen 64-bit p?d

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Message-ID: <Pine.LNX.4.64.0805201357360.24102@blonde.site>
Date:	Tue, 20 May 2008 13:59:47 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Theodore Tso <tytso@....edu>,
	Gabriel C <nix.or.die@...glemail.com>,
	Keith Packard <keithp@...thp.com>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Eric Anholt <eric@...olt.net>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>, airlied@...ux.ie,
	"Barnes, Jesse" <jesse.barnes@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: [PATCH] x86: strengthen 64-bit p?d_bad()

The x86_64 pgd_bad(), pud_bad(), pmd_bad() inlines have differed from
their x86_32 counterparts in a couple of ways: they've been unnecessarily
weak (e.g. letting 0 or 1 count as good), and were typed as unsigned long.
Strengthen them and return int.

The PAE pmd_bad was too weak before, allowing any junk in the upper half;
but got strengthened by the patch correcting its ~PAGE_MASK to ~PTE_MASK.
The PAE pud_bad already said ~PTE_MASK; and since it folds into pgd_bad,
and we don't set the protection bits at that level, it'll do as is.

Signed-off-by: Hugh Dickins <hugh@...itas.com>
---
This could either go in along with Jeremy's PTE_MASK patches, or be
held back for next release - it's independent of them, and not vital.

 include/asm-x86/pgtable_64.h |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/include/asm-x86/pgtable_64.h
+++ b/include/asm-x86/pgtable_64.h
@@ -151,19 +151,19 @@ static inline void native_pgd_clear(pgd_
 
 #ifndef __ASSEMBLY__
 
-static inline unsigned long pgd_bad(pgd_t pgd)
+static inline int pgd_bad(pgd_t pgd)
 {
-	return pgd_val(pgd) & ~(PTE_MASK | _KERNPG_TABLE | _PAGE_USER);
+	return (pgd_val(pgd) & ~(PTE_MASK | _PAGE_USER)) != _KERNPG_TABLE;
 }
 
-static inline unsigned long pud_bad(pud_t pud)
+static inline int pud_bad(pud_t pud)
 {
-	return pud_val(pud) & ~(PTE_MASK | _KERNPG_TABLE | _PAGE_USER);
+	return (pud_val(pud) & ~(PTE_MASK | _PAGE_USER)) != _KERNPG_TABLE;
 }
 
-static inline unsigned long pmd_bad(pmd_t pmd)
+static inline int pmd_bad(pmd_t pmd)
 {
-	return pmd_val(pmd) & ~(PTE_MASK | _KERNPG_TABLE | _PAGE_USER);
+	return (pmd_val(pmd) & ~(PTE_MASK | _PAGE_USER)) != _KERNPG_TABLE;
 }
 
 #define pte_none(x)	(!pte_val((x)))
--
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