[PATCH v6 10/18] x86/power/64: Remove VLA usage

Kees Cook
2018-07-24T16:49:28Z

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 <keescook@chromium.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
---
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