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md: avoid overflow in raid0 calculation with large components 

If a raid0 has a component device larger than 4TB, and is accessed on a 32bit
machines, then as 'chunk' is unsigned long,

   chunk << chunksize_bits

can overflow (this can be as high as the size of the device in KB).  chunk
itself will not overflow (without triggering a BUG).

So change 'chunk' to be 'sector_t, and get rid of the 'BUG' as it becomes
impossible to hit.

Cc: "Jeff Zheng" <Jeff.Zheng@endace.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
NeilBrown 2007-05-23 13:58:09 -07:00 committed by Linus Torvalds
parent 1dbf37e8ad
commit 787f17feb2
1 changed files with 1 additions and 2 deletions
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3
drivers/md/raid0.c
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@ -415,7 +415,7 @@ static int raid0_make_request (request_queue_t *q, struct bio *bio)
raid0_conf_t *conf = mddev_to_conf(mddev);
struct strip_zone *zone;
mdk_rdev_t *tmp_dev;
unsigned long chunk;
sector_t chunk;
sector_t block, rsect;
const int rw = bio_data_dir(bio);
@ -470,7 +470,6 @@ static int raid0_make_request (request_queue_t *q, struct bio *bio)
sector_div(x, zone->nb_dev);
chunk = x;
BUG_ON(x != (sector_t)chunk);
x = block >> chunksize_bits;
tmp_dev = zone->dev[sector_div(x, zone->nb_dev)];