Re: [PATCH v6 10/18] x86/power/64: Remove VLA usage
From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: 2018-07-25 11:32:30
Also in:
dm-devel, linux-block, linux-crypto, linux-pm, lkml, netdev
On Tue, Jul 24, 2018 at 6:49 PM, Kees Cook [off-list ref] wrote:
In the quest to remove all stack VLA usage from the kernel[1], this removes the discouraged use of AHASH_REQUEST_ON_STACK by switching to shash directly and allocating the descriptor in heap memory (which should be fine: the tfm has already been allocated there too). [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook <redacted> Acked-by: Pavel Machek <redacted>
I think I can queue this up if there are no objections from others. Do you want me to do that?
quoted hunk ↗ jump to hunk
--- arch/x86/power/hibernate_64.c | 36 ++++++++++++++++++++--------------- 1 file changed, 21 insertions(+), 15 deletions(-)diff --git a/arch/x86/power/hibernate_64.c b/arch/x86/power/hibernate_64.c index 67ccf64c8bd8..f8e3b668d20b 100644 --- a/arch/x86/power/hibernate_64.c +++ b/arch/x86/power/hibernate_64.c@@ -233,29 +233,35 @@ struct restore_data_record { */ static int get_e820_md5(struct e820_table *table, void *buf) { - struct scatterlist sg; - struct crypto_ahash *tfm; + struct crypto_shash *tfm; + struct shash_desc *desc; int size; int ret = 0; - tfm = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC); + tfm = crypto_alloc_shash("md5", 0, 0); if (IS_ERR(tfm)) return -ENOMEM; - { - AHASH_REQUEST_ON_STACK(req, tfm); - size = offsetof(struct e820_table, entries) + sizeof(struct e820_entry) * table->nr_entries; - ahash_request_set_tfm(req, tfm); - sg_init_one(&sg, (u8 *)table, size); - ahash_request_set_callback(req, 0, NULL, NULL); - ahash_request_set_crypt(req, &sg, buf, size); - - if (crypto_ahash_digest(req)) - ret = -EINVAL; - ahash_request_zero(req); + desc = kmalloc(sizeof(struct shash_desc) + crypto_shash_descsize(tfm), + GFP_KERNEL); + if (!desc) { + ret = -ENOMEM; + goto free_tfm; } - crypto_free_ahash(tfm); + desc->tfm = tfm; + desc->flags = 0; + + size = offsetof(struct e820_table, entries) + + sizeof(struct e820_entry) * table->nr_entries; + + if (crypto_shash_digest(desc, (u8 *)table, size, buf)) + ret = -EINVAL; + + kzfree(desc); + +free_tfm: + crypto_free_shash(tfm); return ret; } --2.17.1