Hi
I would like to see the explanation, why does this patch fix it. i686
allows unaligned access for most instructions, so I wonder how could
adding an alignment fix it.
What is the exact cipher mode that crashes it? How can I reproduce it with
cryptsetup?
Is it possible that something shoots beyond the end of cc->iv_size and the
alignment just masks this bug?
Mikulas
On Mon, 18 Aug 2014, Milan Broz wrote:
> The commit
> 298a9fa08a1577211d42a75e8fc073baef61e0d9
> dm crypt: use per-bio data
> causes OOPS on 32bit i686 architecture
>
> BUG: unable to handle kernel paging request at 20000000
> IP: [<e0fe2433>] clone_endio+0x13/0xe0 [dm_mod]
> ...
>
> [<c1257b61>] bio_endio+0x61/0x90
> [<e142476c>] crypt_dec_pending+0x8c/0xd0 [dm_crypt]
> [<e142666f>] kcryptd_crypt+0x4bf/0x4f0 [dm_crypt]
>
> This patch fixes the issue by aligning per-bio alocated structure size.
>
> Reported-by: Krzysztof Kolasa <kkolasa@xxxxxxxxxx>
> Signed-off-by: Milan Broz <gmazyland@xxxxxxxxx>
> ---
> drivers/md/dm-crypt.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
> index 2785007..33f26a2 100644
> --- a/drivers/md/dm-crypt.c
> +++ b/drivers/md/dm-crypt.c
> @@ -1735,9 +1735,10 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
> goto bad;
> }
>
> - cc->per_bio_data_size = ti->per_bio_data_size =
> - sizeof(struct dm_crypt_io) + cc->dmreq_start +
> - sizeof(struct dm_crypt_request) + cc->iv_size;
> + cc->per_bio_data_size = ALIGN(sizeof(struct dm_crypt_io) + cc->dmreq_start +
> + sizeof(struct dm_crypt_request) + cc->iv_size,
> + ARCH_KMALLOC_MINALIGN);
> + ti->per_bio_data_size = cc->per_bio_data_size;
>
> cc->page_pool = mempool_create_page_pool(MIN_POOL_PAGES, 0);
> if (!cc->page_pool) {
> --
> 2.1.0
>
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