linux-kernel - [PATCH 4.4 23/43] x86/mm: Fix swap entry comment and macro

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20180814171518.654604376@linuxfoundation.org>
Date:   Tue, 14 Aug 2018 19:17:59 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>, Dave Hansen <dave@...1.net>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Luis R. Rodriguez" <mcgrof@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Toshi Kani <toshi.kani@...com>, Ingo Molnar <mingo@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 4.4 23/43] x86/mm: Fix swap entry comment and macro

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Hansen <dave.hansen@...ux.intel.com>

commit ace7fab7a6cdd363a615ec537f2aa94dbc761ee2 upstream

A recent patch changed the format of a swap PTE.

The comment explaining the format of the swap PTE is wrong about
the bits used for the swap type field.  Amusingly, the ASCII art
and the patch description are correct, but the comment itself
is wrong.

As I was looking at this, I also noticed that the
SWP_OFFSET_FIRST_BIT has an off-by-one error.  This does not
really hurt anything.  It just wasted a bit of space in the PTE,
giving us 2^59 bytes of addressable space in our swapfiles
instead of 2^60.  But, it doesn't match with the comments, and it
wastes a bit of space, so fix it.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave@...1.net>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@...e.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Toshi Kani <toshi.kani@...com>
Fixes: 00839ee3b299 ("x86/mm: Move swap offset/type up in PTE to work around erratum")
Link: http://lkml.kernel.org/r/20160810172325.E56AD7DA@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/include/asm/pgtable_64.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -168,7 +168,7 @@ static inline int pgd_large(pgd_t pgd) {
  *
  * |     ...            | 11| 10|  9|8|7|6|5| 4| 3|2|1|0| <- bit number
  * |     ...            |SW3|SW2|SW1|G|L|D|A|CD|WT|U|W|P| <- bit names
- * | OFFSET (14->63) | TYPE (10-13) |0|X|X|X| X| X|X|X|0| <- swp entry
+ * | OFFSET (14->63) | TYPE (9-13)  |0|X|X|X| X| X|X|X|0| <- swp entry
  *
  * G (8) is aliased and used as a PROT_NONE indicator for
  * !present ptes.  We need to start storing swap entries above
@@ -179,7 +179,7 @@ static inline int pgd_large(pgd_t pgd) {
 #define SWP_TYPE_FIRST_BIT (_PAGE_BIT_PROTNONE + 1)
 #define SWP_TYPE_BITS 5
 /* Place the offset above the type: */
-#define SWP_OFFSET_FIRST_BIT (SWP_TYPE_FIRST_BIT + SWP_TYPE_BITS + 1)
+#define SWP_OFFSET_FIRST_BIT (SWP_TYPE_FIRST_BIT + SWP_TYPE_BITS)
 
 #define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS)