linux-kernel - [PATCH v2] net/mlx5e: Refactor switch statements to avoid using uninitialized variables

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Message-Id: <20190710044748.3924-1-natechancellor@gmail.com>
Date:   Tue,  9 Jul 2019 21:47:49 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Saeed Mahameed <saeedm@...lanox.com>,
        Leon Romanovsky <leon@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Boris Pismenny <borisp@...lanox.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH v2] net/mlx5e: Refactor switch statements to avoid using uninitialized variables

clang warns:

drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c:251:2:
warning: variable 'rec_seq_sz' is used uninitialized whenever switch
default is taken [-Wsometimes-uninitialized]
        default:
        ^~~~~~~
drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c:255:46: note:
uninitialized use occurs here
        skip_static_post = !memcmp(rec_seq, &rn_be, rec_seq_sz);
                                                    ^~~~~~~~~~
drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c:239:16: note:
initialize the variable 'rec_seq_sz' to silence this warning
        u16 rec_seq_sz;
                      ^
                       = 0
1 warning generated.

The default case statement should return in tx_post_resync_params like
in fill_static_params_ctx. However, as Nick and Leon point out, the
switch statements converted into if statements to clean up the code a
bit since there is only one cipher supported. Do that to clear up the
code.

Fixes: d2ead1f360e8 ("net/mlx5e: Add kTLS TX HW offload support")
Link: https://github.com/ClangBuiltLinux/linux/issues/590
Suggested-by: Leon Romanovsky <leon@...nel.org>
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---

v1 -> v2:

* Refactor switch statements into if statements

 .../mellanox/mlx5/core/en_accel/ktls_tx.c     | 33 +++++++------------
 1 file changed, 11 insertions(+), 22 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c
index 3f5f4317a22b..ea032f54197e 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c
@@ -25,23 +25,17 @@ static void
 fill_static_params_ctx(void *ctx, struct mlx5e_ktls_offload_context_tx *priv_tx)
 {
 	struct tls_crypto_info *crypto_info = priv_tx->crypto_info;
+	struct tls12_crypto_info_aes_gcm_128 *info;
 	char *initial_rn, *gcm_iv;
 	u16 salt_sz, rec_seq_sz;
 	char *salt, *rec_seq;
 	u8 tls_version;
 
-	switch (crypto_info->cipher_type) {
-	case TLS_CIPHER_AES_GCM_128: {
-		struct tls12_crypto_info_aes_gcm_128 *info =
-			(struct tls12_crypto_info_aes_gcm_128 *)crypto_info;
-
-		EXTRACT_INFO_FIELDS;
-		break;
-	}
-	default:
-		WARN_ON(1);
+	if (WARN_ON(crypto_info->cipher_type != TLS_CIPHER_AES_GCM_128))
 		return;
-	}
+
+	info = (struct tls12_crypto_info_aes_gcm_128 *)crypto_info;
+	EXTRACT_INFO_FIELDS;
 
 	gcm_iv      = MLX5_ADDR_OF(tls_static_params, ctx, gcm_iv);
 	initial_rn  = MLX5_ADDR_OF(tls_static_params, ctx, initial_record_number);
@@ -234,23 +228,18 @@ tx_post_resync_params(struct mlx5e_txqsq *sq,
 		      u64 rcd_sn)
 {
 	struct tls_crypto_info *crypto_info = priv_tx->crypto_info;
+	struct tls12_crypto_info_aes_gcm_128 *info;
 	__be64 rn_be = cpu_to_be64(rcd_sn);
 	bool skip_static_post;
 	u16 rec_seq_sz;
 	char *rec_seq;
 
-	switch (crypto_info->cipher_type) {
-	case TLS_CIPHER_AES_GCM_128: {
-		struct tls12_crypto_info_aes_gcm_128 *info =
-			(struct tls12_crypto_info_aes_gcm_128 *)crypto_info;
+	if (WARN_ON(crypto_info->cipher_type != TLS_CIPHER_AES_GCM_128))
+		return;
 
-		rec_seq = info->rec_seq;
-		rec_seq_sz = sizeof(info->rec_seq);
-		break;
-	}
-	default:
-		WARN_ON(1);
-	}
+	info = (struct tls12_crypto_info_aes_gcm_128 *)crypto_info;
+	rec_seq = info->rec_seq;
+	rec_seq_sz = sizeof(info->rec_seq);
 
 	skip_static_post = !memcmp(rec_seq, &rn_be, rec_seq_sz);
 	if (!skip_static_post)
-- 
2.22.0