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Subject[PATCH 4.4 063/118] dm crypt: fix error with too large bios
4.4-stable review patch.  If anyone has any objections, please let me know.


From: Mikulas Patocka <>

commit 4e870e948fbabf62b78e8410f04c67703e7c816b upstream.

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 <>
Signed-off-by: Mike Snitzer <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/md/dm-crypt.c | 7 +++++++
1 file changed, 7 insertions(+)

--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1920,6 +1920,13 @@ static int crypt_map(struct dm_target *t

+ /*
+ * 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 ablkcipher_request *)(io + 1);

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