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mm: fix wrong vmap address calculations with odd NR_CPUS values

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Commit db64fe0225 ("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 <[email protected]>
Reported-by: Matias A. Fonzo <[email protected]>
Signed-off-by: Clemens Ladisch <[email protected]>
Signed-off-by: Stefan Richter <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Jeremy Fitzhardinge <[email protected]>
Cc: Krzysztof Helt <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: 2.6.28+ <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Clemens Ladisch 2011-06-21 22:09:50 +02:00 • committed by Linus Torvalds
commit f982f91516
1 changed files with 4 additions and 3 deletions
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7
mm/vmalloc.c
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@ -725,9 +725,10 @@ 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)