linux-kernel - [PATCH 1/7] crypto: Fixes uninitialized skcipher_walk use in sm4_aesni_avx

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Message-ID: <DB3PR10MB683563927062940224A92AA3E8A6A@DB3PR10MB6835.EURPRD10.PROD.OUTLOOK.COM>
Date:   Thu,  2 Nov 2023 09:39:25 +0530
From:   Yuran Pereira <yuran.pereira@...mail.com>
To:     linux-crypto@...r.kernel.org, herbert@...dor.apana.org.au
Cc:     Yuran Pereira <yuran.pereira@...mail.com>, davem@...emloft.net,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: [PATCH 1/7] crypto: Fixes uninitialized skcipher_walk use in sm4_aesni_avx_glue

In the following functions:
 - `sm4_avx_ctr_crypt`
 - `sm4_avx_cfb_decrypt`
 - `sm4_cfb_encrypt`
 - `sm4_cbc_encrypt`
 - `sm4_avx_cbc_decrypt`
 - `ecb_do_crypt`

`struct skcipher_walk *walk` is not fully initialized before its use.

Although the call to `skcipher_walk_virt()` and subsequent functions
that this function calls seem to initialize some fields of this struct,

there is a chance that `skcipher_walk_virt()` returns
without fully clearing or properly initializing the `->flags` field
which means that the following flags:
`SKCIPHER_WALK_DIFF`, `SKCIPHER_WALK_COPY`, `SKCIPHER_WALK_SLOW`
could be storing junk values by the time `skcipher_walk_done()` is called.

This could lead to buggy or undefined behaviour since these flags
are checked in `skcipher_walk_done()`:

```C
int skcipher_walk_done(struct skcipher_walk *walk, int err)
{
	...
    if (likely(!(walk->flags & (SKCIPHER_WALK_PHYS |
        SKCIPHER_WALK_SLOW |
        SKCIPHER_WALK_COPY |
        SKCIPHER_WALK_DIFF)))) {
    ...
}
```

To prevent this, this patch ensures that instances of `struct skcipher_walk`
are correctly initialized prior to their use.

Addresses-Coverity-IDs: 1491520, 1491533, 1491610, 1491651, 1491715,
                        1491774 ("Unintialized scalar variable")
Signed-off-by: Yuran Pereira <yuran.pereira@...mail.com>
---
 arch/x86/crypto/sm4_aesni_avx_glue.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/crypto/sm4_aesni_avx_glue.c b/arch/x86/crypto/sm4_aesni_avx_glue.c
index 7800f77d68ad..4117c6f787e2 100644
--- a/arch/x86/crypto/sm4_aesni_avx_glue.c
+++ b/arch/x86/crypto/sm4_aesni_avx_glue.c
@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/crypto.h>
 #include <linux/kernel.h>
+#include <linux/string.h>
 #include <asm/simd.h>
 #include <crypto/internal/simd.h>
 #include <crypto/internal/skcipher.h>
@@ -44,6 +45,7 @@ static int ecb_do_crypt(struct skcipher_request *req, const u32 *rkey)
 	unsigned int nbytes;
 	int err;
 
+	memset(&walk, 0, sizeof(walk));
 	err = skcipher_walk_virt(&walk, req, false);
 
 	while ((nbytes = walk.nbytes) > 0) {
@@ -98,6 +100,7 @@ int sm4_cbc_encrypt(struct skcipher_request *req)
 	unsigned int nbytes;
 	int err;
 
+	memset(&walk, 0, sizeof(walk));
 	err = skcipher_walk_virt(&walk, req, false);
 
 	while ((nbytes = walk.nbytes) > 0) {
@@ -132,6 +135,7 @@ int sm4_avx_cbc_decrypt(struct skcipher_request *req,
 	unsigned int nbytes;
 	int err;
 
+	memset(&walk, 0, sizeof(walk));
 	err = skcipher_walk_virt(&walk, req, false);
 
 	while ((nbytes = walk.nbytes) > 0) {
@@ -196,6 +200,7 @@ int sm4_cfb_encrypt(struct skcipher_request *req)
 	unsigned int nbytes;
 	int err;
 
+	memset(&walk, 0, sizeof(walk));
 	err = skcipher_walk_virt(&walk, req, false);
 
 	while ((nbytes = walk.nbytes) > 0) {
@@ -238,6 +243,7 @@ int sm4_avx_cfb_decrypt(struct skcipher_request *req,
 	unsigned int nbytes;
 	int err;
 
+	memset(&walk, 0, sizeof(walk));
 	err = skcipher_walk_virt(&walk, req, false);
 
 	while ((nbytes = walk.nbytes) > 0) {
@@ -307,6 +313,7 @@ int sm4_avx_ctr_crypt(struct skcipher_request *req,
 	unsigned int nbytes;
 	int err;
 
+	memset(&walk, 0, sizeof(walk));
 	err = skcipher_walk_virt(&walk, req, false);
 
 	while ((nbytes = walk.nbytes) > 0) {
-- 
2.25.1