[PATCH] net/mlx5e: Return in default case statement in tx_post_resync_params

[PATCH] net/mlx5e: Return in default case statement in tx_post_resync_params

[Nathan Chancellor]

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.

This case statement was clearly designed to be one that should not be
hit during runtime because of the WARN_ON statement so just return early
to prevent copying uninitialized memory up into rn_be.

Fixes: d2ead1f360e8 ("net/mlx5e: Add kTLS TX HW offload support")
Link: https://github.com/ClangBuiltLinux/linux/issues/590
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c | 1 +
 1 file changed, 1 insertion(+)

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..5c08891806f0 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
@@ -250,6 +250,7 @@ tx_post_resync_params(struct mlx5e_txqsq *sq,
 	}
 	default:
 		WARN_ON(1);
+		return;
 	}
 
 	skip_static_post = !memcmp(rec_seq, &rn_be, rec_seq_sz);
-- 
2.22.0

Re: [PATCH] net/mlx5e: Return in default case statement in tx_post_resync_params

[Nick Desaulniers]

On Mon, Jul 8, 2019 at 4:13 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> 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.
>
> This case statement was clearly designed to be one that should not be
> hit during runtime because of the WARN_ON statement so just return early
> to prevent copying uninitialized memory up into rn_be.
>
> Fixes: d2ead1f360e8 ("net/mlx5e: Add kTLS TX HW offload support")
> Link: https://github.com/ClangBuiltLinux/linux/issues/590
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c | 1 +
>  1 file changed, 1 insertion(+)
>
> 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..5c08891806f0 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
> @@ -250,6 +250,7 @@ tx_post_resync_params(struct mlx5e_txqsq *sq,
>         }
>         default:
>                 WARN_ON(1);
> +               return;
>         }

hmm...a switch statement with a single case is a code smell.  How
about a single conditional with early return?  Then the "meat" of the
happy path doesn't need an additional level of indentation.
-- 
Thanks,
~Nick Desaulniers

Re: [PATCH] net/mlx5e: Return in default case statement in tx_post_resync_params

[Nathan Chancellor]

On Tue, Jul 09, 2019 at 03:44:59PM -0700, Nick Desaulniers wrote:
> On Mon, Jul 8, 2019 at 4:13 PM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > 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.
> >
> > This case statement was clearly designed to be one that should not be
> > hit during runtime because of the WARN_ON statement so just return early
> > to prevent copying uninitialized memory up into rn_be.
> >
> > Fixes: d2ead1f360e8 ("net/mlx5e: Add kTLS TX HW offload support")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/590
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > ---
> >  drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > 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..5c08891806f0 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
> > @@ -250,6 +250,7 @@ tx_post_resync_params(struct mlx5e_txqsq *sq,
> >         }
> >         default:
> >                 WARN_ON(1);
> > +               return;
> >         }
> 
> hmm...a switch statement with a single case is a code smell.  How
> about a single conditional with early return?  Then the "meat" of the
> happy path doesn't need an additional level of indentation.
> -- 
> Thanks,
> ~Nick Desaulniers

I assume that the reason for this is there may be other cipher types
added in the future? I suppose the maintainers can give more clarity to
that.

Furthermore, if they want the switch statements to remain, it looks like
fill_static_params_ctx also returns in the default statement so it seems
like this is the right fix.

Cheers,
Nathan

Re: [PATCH] net/mlx5e: Return in default case statement in tx_post_resync_params

[Leon Romanovsky]

On Tue, Jul 09, 2019 at 04:10:24PM -0700, Nathan Chancellor wrote:
> On Tue, Jul 09, 2019 at 03:44:59PM -0700, Nick Desaulniers wrote:
> > On Mon, Jul 8, 2019 at 4:13 PM Nathan Chancellor
> > <natechancellor@gmail.com> wrote:
> > >
> > > 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.
> > >
> > > This case statement was clearly designed to be one that should not be
> > > hit during runtime because of the WARN_ON statement so just return early
> > > to prevent copying uninitialized memory up into rn_be.
> > >
> > > Fixes: d2ead1f360e8 ("net/mlx5e: Add kTLS TX HW offload support")
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/590
> > > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > > ---
> > >  drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > 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..5c08891806f0 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
> > > @@ -250,6 +250,7 @@ tx_post_resync_params(struct mlx5e_txqsq *sq,
> > >         }
> > >         default:
> > >                 WARN_ON(1);
> > > +               return;
> > >         }
> >
> > hmm...a switch statement with a single case is a code smell.  How
> > about a single conditional with early return?  Then the "meat" of the
> > happy path doesn't need an additional level of indentation.
> > --
> > Thanks,
> > ~Nick Desaulniers
>
> I assume that the reason for this is there may be other cipher types
> added in the future? I suppose the maintainers can give more clarity to
> that.

Our devices supports extra ciphers, for example TLS_CIPHER_AES_GCM_256.
So I assume this was the reason for switch<->case, but because such
implementation doesn't exist in any driver, I recommend to rewrite the
code to have "if" statement and return early.

>
> Furthermore, if they want the switch statements to remain, it looks like
> fill_static_params_ctx also returns in the default statement so it seems
> like this is the right fix.
>
> Cheers,
> Nathan

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

[Nathan Chancellor]

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@kernel.org>
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.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

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

[Leon Romanovsky]

On Tue, Jul 09, 2019 at 09:47:49PM -0700, Nathan Chancellor wrote:
> 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@kernel.org>
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.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(-)
>

Thanks,
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>

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

[David Miller]

I applied your simpler addition of the return statement so that I could
get the net-next pull request out tonight, just FYI...

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

[Nathan Chancellor]

On Tue, Jul 09, 2019 at 10:36:57PM -0700, David Miller wrote:
> 
> I applied your simpler addition of the return statement so that I could
> get the net-next pull request out tonight, just FYI...

Thanks for the heads up, I'll spin up a v3 just focusing on the
refactoring.

Cheers,
Nathan

[PATCH net-next v3] net/mlx5e: Convert single case statement switch statements into if statements

[Nathan Chancellor]

During the review of commit 1ff2f0fa450e ("net/mlx5e: Return in default
case statement in tx_post_resync_params"), Leon and Nick pointed out
that the switch statements can be converted to single if statements
that return early so that the code is easier to follow.

Suggested-by: Leon Romanovsky <leon@kernel.org>
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---

v1 -> v2:

* Refactor switch statements into if statements

v2 -> v3:

* Rebase on net-next after v1 was already applied, patch just refactors
  switch statements to if statements.

 .../mellanox/mlx5/core/en_accel/ktls_tx.c     | 34 ++++++-------------
 1 file changed, 11 insertions(+), 23 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 5c08891806f0..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);
@@ -234,24 +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;
-
-		rec_seq = info->rec_seq;
-		rec_seq_sz = sizeof(info->rec_seq);
-		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;
+	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

Re: [PATCH net-next v3] net/mlx5e: Convert single case statement switch statements into if statements

[Leon Romanovsky]

On Tue, Jul 09, 2019 at 11:06:15PM -0700, Nathan Chancellor wrote:
> During the review of commit 1ff2f0fa450e ("net/mlx5e: Return in default
> case statement in tx_post_resync_params"), Leon and Nick pointed out
> that the switch statements can be converted to single if statements
> that return early so that the code is easier to follow.
>
> Suggested-by: Leon Romanovsky <leon@kernel.org>
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---

Thanks again,
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>

Re: [PATCH net-next v3] net/mlx5e: Convert single case statement switch statements into if statements

[David Miller]

From: Nathan Chancellor <natechancellor@gmail.com>
Date: Tue,  9 Jul 2019 23:06:15 -0700

> During the review of commit 1ff2f0fa450e ("net/mlx5e: Return in default
> case statement in tx_post_resync_params"), Leon and Nick pointed out
> that the switch statements can be converted to single if statements
> that return early so that the code is easier to follow.
> 
> Suggested-by: Leon Romanovsky <leon@kernel.org>
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

Applied, thanks for following up Nathan.