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[173.164.112.133]) by smtp.gmail.com with ESMTPSA id l70-v6sm24096616pge.64.2018.07.16.21.21.52 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 16 Jul 2018 21:21:53 -0700 (PDT) From: Kees Cook To: Herbert Xu Cc: Kees Cook , Arnd Bergmann , Eric Biggers , "Gustavo A. R. Silva" , Alasdair Kergon , Giovanni Cabiddu , Lars Persson , Mike Snitzer , Rabin Vincent , Tim Chen , linux-crypto@vger.kernel.org, qat-linux@intel.com, dm-devel@redhat.com, linux-kernel@vger.kernel.org Subject: [PATCH v5 04/11] dm integrity: Remove VLA usage Date: Mon, 16 Jul 2018 21:21:43 -0700 Message-Id: <20180717042150.37761-5-keescook@chromium.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180717042150.37761-1-keescook@chromium.org> References: <20180717042150.37761-1-keescook@chromium.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In the quest to remove all stack VLA usage from the kernel[1], this uses the new SHASH_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 --- drivers/md/dm-integrity.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c index 86438b2f10dd..85e8ce1625a2 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[SHASH_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[SHASH_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; @@ -1466,7 +1477,7 @@ static bool __journal_read_write(struct dm_integrity_io *dio, struct bio *bio, } 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(SHASH_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))) { @@ -1516,7 +1527,7 @@ static bool __journal_read_write(struct dm_integrity_io *dio, struct bio *bio, 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[SHASH_MAX_DIGESTSIZE]; integrity_sector_checksum(ic, logical_sector, (char *)js, checksums_onstack); memcpy(journal_entry_tag(ic, je), checksums_onstack, ic->tag_size); } else @@ -1937,7 +1948,7 @@ 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, SHASH_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); -- 2.17.1