x86/power/hibernate_64: Remove VLA usage

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).

Link: 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>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/arch/x86/power/hibernate_64.c b/arch/x86/power/hibernate_64.c
index 67ccf64c8bd83346dce7bfb7342f19a4309d5364..f8e3b668d20b9b2cde3ff31ed6131efbf7273b4a 100644 (file)
--- 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;
 }