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dm crypt: fix error with too large bios

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When dm-crypt processes writes, it allocates a new bio in
crypt_alloc_buffer().  The bio is allocated from a bio set and it can
have at most BIO_MAX_PAGES vector entries, however the incoming bio can be
larger (e.g. if it was allocated by bcache).  If the incoming bio is
larger, bio_alloc_bioset() fails and an error is returned.

To avoid the error, we test for a too large bio in the function
crypt_map() and use dm_accept_partial_bio() to split the bio.
dm_accept_partial_bio() trims the current bio to the desired size and
asks DM core to send another bio with the rest of the data.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v3.16+
This commit is contained in:
Mikulas Patocka 2016-08-30 16:38:42 -04:00 committed by Mike Snitzer
parent 91e630d9ae
commit 4e870e948f
1 changed files with 7 additions and 0 deletions
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7
drivers/md/dm-crypt.c
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@ -1924,6 +1924,13 @@ static int crypt_map(struct dm_target *ti, struct bio *bio)
return DM_MAPIO_REMAPPED;
}
/*
* Check if bio is too large, split as needed.
*/
if (unlikely(bio->bi_iter.bi_size > (BIO_MAX_PAGES << PAGE_SHIFT)) &&
bio_data_dir(bio) == WRITE)
dm_accept_partial_bio(bio, ((BIO_MAX_PAGES << PAGE_SHIFT) >> SECTOR_SHIFT));
io = dm_per_bio_data(bio, cc->per_bio_data_size);
crypt_io_init(io, cc, bio, dm_target_offset(ti, bio->bi_iter.bi_sector));
io->ctx.req = (struct skcipher_request *)(io + 1);