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

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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.

Reported-by: Michael Tokarev <mjt@tls.msk.ru>
Tested-by: Michael Tokarev <mjt@tls.msk.ru>
Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka 2021-05-07 11:38:10 -04:00 committed by Mike Snitzer
parent 6efb943b86
commit 7ee06ddc40
1 changed files with 2 additions and 3 deletions
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5
drivers/md/dm-snap.c
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@ -855,12 +855,11 @@ static int dm_add_exception(void *context, chunk_t old, chunk_t new)
static uint32_t __minimum_chunk_size(struct origin *o) static uint32_t __minimum_chunk_size(struct origin *o)
{ {
struct dm_snapshot *snap; struct dm_snapshot *snap;
unsigned chunk_size = 0; unsigned chunk_size = rounddown_pow_of_two(UINT_MAX);
if (o) if (o)
list_for_each_entry(snap, &o->snapshots, list) list_for_each_entry(snap, &o->snapshots, list)
chunk_size = min_not_zero(chunk_size, chunk_size = min(chunk_size, snap->store->chunk_size);
snap->store->chunk_size);
return (uint32_t) chunk_size; return (uint32_t) chunk_size;
} }