Subject: Re: [bug] crypto/vmx/p8_ghash memory corruption in 4.8-rc7

From: Marcelo Cerri <[email-masked]>
Date: Tue, 27 Sep 2016 16:46:44 -0300

Jan, 

Can you check if the problem occurs with this patch?

---
 drivers/crypto/vmx/ghash.c | 28 +++++++++++++++++-----------
 drivers/crypto/vmx/vmx.c   |  9 +++++++++
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/drivers/crypto/vmx/ghash.c b/drivers/crypto/vmx/ghash.c
index 6c999cb0..033aba1 100644
--- a/drivers/crypto/vmx/ghash.c
+++ b/drivers/crypto/vmx/ghash.c
@@ -36,6 +36,8 @@
 #define GHASH_DIGEST_SIZE (16)
 #define GHASH_KEY_LEN (16)
 
+#define GHASH_FALLBACK_ALG "ghash-generic"
+
 void gcm_init_p8(u128 htable[16], const u64 Xi[2]);
 void gcm_gmult_p8(u64 Xi[2], const u128 htable[16]);
 void gcm_ghash_p8(u64 Xi[2], const u128 htable[16],
@@ -53,18 +55,26 @@ struct p8_ghash_desc_ctx {
 	struct shash_desc fallback_desc;
 };
 
+int p8_ghash_fallback_descsize(void)
+{
+	int descsize;
+	struct crypto_shash *fallback;
+	fallback = crypto_alloc_shash(GHASH_FALLBACK_ALG, 0,
+				      CRYPTO_ALG_NEED_FALLBACK);
+	if (IS_ERR(fallback)) {
+		return PTR_ERR(fallback);
+	}
+	descsize = crypto_shash_descsize(fallback);
+	crypto_free_shash(fallback);
+	return descsize;
+}
+
 static int p8_ghash_init_tfm(struct crypto_tfm *tfm)
 {
-	const char *alg;
+	const char *alg = GHASH_FALLBACK_ALG;
 	struct crypto_shash *fallback;
-	struct crypto_shash *shash_tfm = __crypto_shash_cast(tfm);
 	struct p8_ghash_ctx *ctx = crypto_tfm_ctx(tfm);
 
-	if (!(alg = crypto_tfm_alg_name(tfm))) {
-		printk(KERN_ERR "Failed to get algorithm name.\n");
-		return -ENOENT;
-	}
-
 	fallback = crypto_alloc_shash(alg, 0, CRYPTO_ALG_NEED_FALLBACK);
 	if (IS_ERR(fallback)) {
 		printk(KERN_ERR
@@ -79,10 +89,6 @@ static int p8_ghash_init_tfm(struct crypto_tfm *tfm)
 			       crypto_shash_get_flags((struct crypto_shash
 						       *) tfm));
 	ctx->fallback = fallback;
-
-	shash_tfm->descsize = sizeof(struct p8_ghash_desc_ctx)
-	    + crypto_shash_descsize(fallback);
-
 	return 0;
 }
 
diff --git a/drivers/crypto/vmx/vmx.c b/drivers/crypto/vmx/vmx.c
index 31a98dc..8a51149 100644
--- a/drivers/crypto/vmx/vmx.c
+++ b/drivers/crypto/vmx/vmx.c
@@ -28,6 +28,8 @@
 #include <asm/cputable.h>
 #include <crypto/internal/hash.h>
 
+int p8_ghash_fallback_descsize(void);
+
 extern struct shash_alg p8_ghash_alg;
 extern struct crypto_alg p8_aes_alg;
 extern struct crypto_alg p8_aes_cbc_alg;
@@ -45,6 +47,7 @@ int __init p8_init(void)
 {
 	int ret = 0;
 	struct crypto_alg **alg_it;
+	int ghash_descsize;
 
 	for (alg_it = algs; *alg_it; alg_it++) {
 		ret = crypto_register_alg(*alg_it);
@@ -59,6 +62,12 @@ int __init p8_init(void)
 	if (ret)
 		return ret;
 
+	ghash_descsize = p8_ghash_fallback_descsize();
+	if (ghash_descsize < 0) {
+		printk(KERN_ERR "Cannot get descsize for p8_ghash fallback\n");
+		return ghash_descsize;
+	}
+	p8_ghash_alg.descsize += ghash_descsize;
 	ret = crypto_register_shash(&p8_ghash_alg);
 	if (ret) {
 		for (alg_it = algs; *alg_it; alg_it++)
-- 
2.7.4