Hi Yeongjin,
On Thu, Mar 16, 2023 at 12:18:42PM +0900, Yeongjin Gil wrote:
> In verity_work(), the return value of verity_verify_io() is converted to
> blk_status and passed to verity_finish_io(). BTW, when a bit is set in
> v->validated_blocks, verity_verify_io() skips verification regardless of
> I/O error for the corresponding bio. In this case, the I/O error could
> not be returned properly, and as a result, there is a problem that
> abnormal data could be read for the corresponding block.
>
> To fix this problem, when an I/O error occurs, do not skip verification
> even if the bit related is set in v->validated_blocks.
>
> Fixes: 843f38d382b1 ("dm verity: add 'check_at_most_once' option to only validate hashes once")
>
> Signed-off-by: Sungjong Seo <sj1557.seo@xxxxxxxxxxx>
> Signed-off-by: Yeongjin Gil <youngjin.gil@xxxxxxxxxxx>
> ---
> drivers/md/dm-verity-target.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
> index ade83ef3b439..9316399b920e 100644
> --- a/drivers/md/dm-verity-target.c
> +++ b/drivers/md/dm-verity-target.c
> @@ -523,7 +523,7 @@ static int verity_verify_io(struct dm_verity_io *io)
> sector_t cur_block = io->block + b;
> struct ahash_request *req = verity_io_hash_req(v, io);
>
> - if (v->validated_blocks &&
> + if (v->validated_blocks && bio->bi_status == BLK_STS_OK &&
> likely(test_bit(cur_block, v->validated_blocks))) {
> verity_bv_skip_block(v, io, iter);
> continue;
Thanks for sending this patch! This looks like a correct fix, but I have some
comments:
* Using "check_at_most_once" is strongly discouraged, as it reduces security.
If you are using check_at_most_once to improve performance at the cost of
reduced security, please consider that very recently, dm-verity performance
has significantly improved due to the removal of the WQ_UNBOUND workqueue flag
which was causing significant I/O latency. See commit c25da5b7baf1
("dm verity: stop using WQ_UNBOUND for verify_wq").
* I think your commit message does not explain a key aspect of the problem which
is why is verity even attempted when the underlying I/O has failed? This
appears to be because of the Forward Error Correction (FEC) feature. So, this
issue is specific to the case where both FEC and check_at_most_once is used.
Can you make your commit message explain this?
* This patch does not appear to have been received by the dm-devel mailing list,
which is the list where dm-verity patches should be reviewed on. It doesn't
show up in the archive at https://lore.kernel.org/dm-devel. Also, I'm
subscribed to dm-devel and I didn't receive this patch in my inbox. (I had to
download it from https://lore.kernel.org/lkml instead.) Did you receive a
bounce message when you sent this patch?
* Please add 'Cc: stable@xxxxxxxxxxxxxxx' to the commit message, just below the
Fixes line, as per Documentation/process/stable-kernel-rules.rst. This will
ensure that the fix will be backported to the stable kernels.
* "Signed-off-by: Sungjong Seo <sj1557.seo@xxxxxxxxxxx>" does not have a
corresponding Author or Co-developed-line, which is not allowed. Did you mean
to list Sungjong as the Author or as a co-author?
* No blank line between Fixes and the Signed-off-by line(s), please.
Thanks!
- Eric
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