On Tue, Aug 07 2018 at 5:18pm -0400, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > In the quest to remove all stack VLA usage from the kernel[1], this uses > the new HASH_MAX_DIGESTSIZE from the crypto layer to allocate the upper > bounds on stack usage. > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > --- > drivers/md/dm-integrity.c | 23 +++++++++++++++++------ > drivers/md/dm-verity-fec.c | 5 ++++- > 2 files changed, 21 insertions(+), 7 deletions(-) > > diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c > index 86438b2f10dd..884edd7cf1d0 100644 > --- a/drivers/md/dm-integrity.c > +++ b/drivers/md/dm-integrity.c > @@ -521,7 +521,12 @@ static void section_mac(struct dm_integrity_c *ic, unsigned section, __u8 result > } > memset(result + size, 0, JOURNAL_MAC_SIZE - size); > } else { > - __u8 digest[size]; > + __u8 digest[HASH_MAX_DIGESTSIZE]; > + > + if (WARN_ON(size > sizeof(digest))) { > + dm_integrity_io_error(ic, "digest_size", -EINVAL); > + goto err; > + } > r = crypto_shash_final(desc, digest); > if (unlikely(r)) { > dm_integrity_io_error(ic, "crypto_shash_final", r); > @@ -1244,7 +1249,7 @@ static void integrity_metadata(struct work_struct *w) > struct bio *bio = dm_bio_from_per_bio_data(dio, sizeof(struct dm_integrity_io)); > char *checksums; > unsigned extra_space = unlikely(digest_size > ic->tag_size) ? digest_size - ic->tag_size : 0; > - char checksums_onstack[ic->tag_size + extra_space]; > + char checksums_onstack[HASH_MAX_DIGESTSIZE]; > unsigned sectors_to_process = dio->range.n_sectors; > sector_t sector = dio->range.logical_sector; > > @@ -1253,8 +1258,14 @@ static void integrity_metadata(struct work_struct *w) > > checksums = kmalloc((PAGE_SIZE >> SECTOR_SHIFT >> ic->sb->log2_sectors_per_block) * ic->tag_size + extra_space, > GFP_NOIO | __GFP_NORETRY | __GFP_NOWARN); > - if (!checksums) > + if (!checksums) { > checksums = checksums_onstack; > + if (WARN_ON(extra_space && > + digest_size > sizeof(checksums_onstack))) { > + r = -EINVAL; > + goto error; > + } > + } > > __bio_for_each_segment(bv, bio, iter, dio->orig_bi_iter) { > unsigned pos; Given the length of the kmalloc() just prior to this new WARN_ON() line I'm not seeing why you've elected to split the WARN_ON across multiple lines. But that style nit aside: Acked-by: Mike Snitzer <snitzer@xxxxxxxxxx>
