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authorLin Feng <linfeng@cn.fujitsu.com>2013-01-11 14:31:44 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-01-11 14:54:54 -0800
commitc0232ae861df679092c15960b6cd9f589d9b7177 (patch)
tree9b4bf9d12da79ac04d5fa04f45d8fc90ced18dc5 /mm
parent552f0cc72aadfc8657876ce310e7a8dc37529536 (diff)
mm: memblock: fix wrong memmove size in memblock_merge_regions()
The memmove span covers from (next+1) to the end of the array, and the index of next is (i+1), so the index of (next+1) is (i+2). So the size of remaining array elements is (type->cnt - (i + 2)). Since the remaining elements of the memblock array are move forward by one element and there is only one additional element caused by this bug. So there won't be any write overflow here but read overflow. It may read one more element out of the array address if the array happens to be full. Commonly it doesn't matter at all but if the array happens to be located at the end a memblock, it may cause a invalid read operation for the physical address doesn't exist. There are 2 *happens to be* here, so I think the probability is quite low, I don't know if any guy is haunted by this bug before. Mostly I think it's user-invisible. Signed-off-by: Lin Feng <linfeng@cn.fujitsu.com> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memblock.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/memblock.c b/mm/memblock.c
index 625905523c2..88adc8afb61 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -314,7 +314,8 @@ static void __init_memblock memblock_merge_regions(struct memblock_type *type)
}
this->size += next->size;
- memmove(next, next + 1, (type->cnt - (i + 1)) * sizeof(*next));
+ /* move forward from next + 1, index of which is i + 2 */
+ memmove(next, next + 1, (type->cnt - (i + 2)) * sizeof(*next));
type->cnt--;
}
}