dm: Remove VLA usage from hashes

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@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index 3788785..5c1197b 100644 (file)
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -559,7 +559,12 @@ 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);
@@ -1324,7 +1329,7 @@ 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;
 
@@ -1333,8 +1338,14 @@ 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;
@@ -1546,7 +1557,7 @@ retry_kmap:
                                } while (++s < ic->sectors_per_block);
 #ifdef INTERNAL_VERIFY
                                if (ic->internal_hash) {
-                                       char checksums_onstack[max(crypto_shash_digestsize(ic->internal_hash), ic->tag_size)];
+                                       char checksums_onstack[max(HASH_MAX_DIGESTSIZE, MAX_TAG_SIZE)];
 
                                        integrity_sector_checksum(ic, logical_sector, mem + bv.bv_offset, checksums_onstack);
                                        if (unlikely(memcmp(checksums_onstack, journal_entry_tag(ic, je), ic->tag_size))) {
@@ -1596,7 +1607,7 @@ retry_kmap:
                                if (ic->internal_hash) {
                                        unsigned digest_size = crypto_shash_digestsize(ic->internal_hash);
                                        if (unlikely(digest_size > ic->tag_size)) {
-                                               char checksums_onstack[digest_size];
+                                               char checksums_onstack[HASH_MAX_DIGESTSIZE];
                                                integrity_sector_checksum(ic, logical_sector, (char *)js, checksums_onstack);
                                                memcpy(journal_entry_tag(ic, je), checksums_onstack, ic->tag_size);
                                        } else
@@ -2023,7 +2034,7 @@ static void do_journal_write(struct dm_integrity_c *ic, unsigned write_start,
                                    unlikely(from_replay) &&
 #endif
                                    ic->internal_hash) {
-                                       char test_tag[max(crypto_shash_digestsize(ic->internal_hash), ic->tag_size)];
+                                       char test_tag[max_t(size_t, HASH_MAX_DIGESTSIZE, MAX_TAG_SIZE)];
 
                                        integrity_sector_checksum(ic, sec + ((l - j) << ic->sb->log2_sectors_per_block),
                                                                  (char *)access_journal_data(ic, i, l), test_tag);

diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c
index 684af08..0ce04e5 100644 (file)
--- a/drivers/md/dm-verity-fec.c
+++ b/drivers/md/dm-verity-fec.c
@@ -212,12 +212,15 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
        struct dm_verity_fec_io *fio = fec_io(io);
        u64 block, ileaved;
        u8 *bbuf, *rs_block;
-       u8 want_digest[v->digest_size];
+       u8 want_digest[HASH_MAX_DIGESTSIZE];
        unsigned n, k;
 
        if (neras)
                *neras = 0;
 
+       if (WARN_ON(v->digest_size > sizeof(want_digest)))
+               return -EINVAL;
+
        /*
         * read each of the rsn data blocks that are part of the RS block, and
         * interleave contents to available bufs