lkml.org 
[lkml]   [2012]   [May]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[34-longterm 163/179] mm: fix wrong vmap address calculations with odd NR_CPUS values
Date
From: Clemens Ladisch <clemens@ladisch.de>

-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------
commit f982f91516fa4cfd9d20518833cd04ad714585be upstream.

Commit db64fe02258f ("mm: rewrite vmap layer") introduced code that does
address calculations under the assumption that VMAP_BLOCK_SIZE is a
power of two. However, this might not be true if CONFIG_NR_CPUS is not
set to a power of two.

Wrong vmap_block index/offset values could lead to memory corruption.
However, this has never been observed in practice (or never been
diagnosed correctly); what caught this was the BUG_ON in vb_alloc() that
checks for inconsistent vmap_block indices.

To fix this, ensure that VMAP_BLOCK_SIZE always is a power of two.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=31572
Reported-by: Pavel Kysilka <goldenfish@linuxsoft.cz>
Reported-by: Matias A. Fonzo <selk@dragora.org>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
mm/vmalloc.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 20a402c..d44abdd 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -671,9 +671,10 @@ static void free_unmap_vmap_area_addr(unsigned long addr)
#define VMAP_BBMAP_BITS_MIN (VMAP_MAX_ALLOC*2)
#define VMAP_MIN(x, y) ((x) < (y) ? (x) : (y)) /* can't use min() */
#define VMAP_MAX(x, y) ((x) > (y) ? (x) : (y)) /* can't use max() */
-#define VMAP_BBMAP_BITS VMAP_MIN(VMAP_BBMAP_BITS_MAX, \
- VMAP_MAX(VMAP_BBMAP_BITS_MIN, \
- VMALLOC_PAGES / NR_CPUS / 16))
+#define VMAP_BBMAP_BITS \
+ VMAP_MIN(VMAP_BBMAP_BITS_MAX, \
+ VMAP_MAX(VMAP_BBMAP_BITS_MIN, \
+ VMALLOC_PAGES / roundup_pow_of_two(NR_CPUS) / 16))

#define VMAP_BLOCK_SIZE (VMAP_BBMAP_BITS * PAGE_SIZE)

--
1.7.9.6


\
 
 \ /
  Last update: 2012-05-15 07:01    [from the cache]
©2003-2011 Jasper Spaans