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dm snapshot: properly fix a crash when an origin has no snapshots 

commit 7e768532b2396bcb7fbf6f82384b85c0f1d2f197 upstream.

If an origin target has no snapshots, o->split_boundary is set to 0.
This causes BUG_ON(sectors <= 0) in block/bio.c:bio_split().

Fix this by initializing chunk_size, and in turn split_boundary, to
rounddown_pow_of_two(UINT_MAX) -- the largest power of two that fits
into "unsigned" type.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mikulas Patocka 2021-05-25 13:17:19 -04:00 committed by Greg Kroah-Hartman
parent b06fe11243
commit d65ec240b3
1 changed files with 1 additions and 1 deletions
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2
drivers/md/dm-snap.c
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@ -854,7 +854,7 @@ static int dm_add_exception(void *context, chunk_t old, chunk_t new)
static uint32_t __minimum_chunk_size(struct origin *o)
{
struct dm_snapshot *snap;
unsigned chunk_size = 0;
unsigned chunk_size = rounddown_pow_of_two(UINT_MAX);
if (o)
list_for_each_entry(snap, &o->snapshots, list)