[PATCH] can: janz-ican3: initialize dlc variable

[PATCH] can: janz-ican3: initialize dlc variable

[trix]

From: Tom Rix <trix@redhat.com>

Clang static analysis reports this problem
janz-ican3.c:1311:2: warning: Undefined or garbage value returned to caller
        return dlc;
        ^~~~~~~~~~

dlc is only set with this conditional
	if (!(cf->can_id & CAN_RTR_FLAG))
		dlc = cf->len;

But is always returned.  So initialize dlc to 0.

Fixes: cc4b08c31b5c ("can: do not increase tx_bytes statistics for RTR frames")
Signed-off-by: Tom Rix <trix@redhat.com>
---
 drivers/net/can/janz-ican3.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/can/janz-ican3.c b/drivers/net/can/janz-ican3.c
index 5b677af5f2a41..808c105cf8f7e 100644
--- a/drivers/net/can/janz-ican3.c
+++ b/drivers/net/can/janz-ican3.c
@@ -1285,7 +1285,7 @@ static unsigned int ican3_get_echo_skb(struct ican3_dev *mod)
 {
 	struct sk_buff *skb = skb_dequeue(&mod->echoq);
 	struct can_frame *cf;
-	u8 dlc;
+	u8 dlc = 0;
 
 	/* this should never trigger unless there is a driver bug */
 	if (!skb) {
-- 
2.26.3

Re: [PATCH] can: janz-ican3: initialize dlc variable

[Vincent MAILHOL]

On Sat. 8 Jan 2022 à 23:33, <trix@redhat.com> wrote:
> From: Tom Rix <trix@redhat.com>
>
> Clang static analysis reports this problem
> janz-ican3.c:1311:2: warning: Undefined or garbage value returned to caller
>         return dlc;
>         ^~~~~~~~~~
>
> dlc is only set with this conditional
>         if (!(cf->can_id & CAN_RTR_FLAG))
>                 dlc = cf->len;
>
> But is always returned.  So initialize dlc to 0.

Yes. The actual intent is to return a length of 0 for RTR frames.

> Fixes: cc4b08c31b5c ("can: do not increase tx_bytes statistics for RTR frames")
> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
>  drivers/net/can/janz-ican3.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/can/janz-ican3.c b/drivers/net/can/janz-ican3.c
> index 5b677af5f2a41..808c105cf8f7e 100644
> --- a/drivers/net/can/janz-ican3.c
> +++ b/drivers/net/can/janz-ican3.c
> @@ -1285,7 +1285,7 @@ static unsigned int ican3_get_echo_skb(struct ican3_dev *mod)
>  {
>         struct sk_buff *skb = skb_dequeue(&mod->echoq);
>         struct can_frame *cf;
> -       u8 dlc;
> +       u8 dlc = 0;
>
>         /* this should never trigger unless there is a driver bug */
>         if (!skb) {
> --
> 2.26.3

I missed that when writing the patch.

I thought that I did my due diligence by running a "make W=1"
with GCC but I did not catch the error. I should have been more
precocious and run a "make W=2".

Thank you.

Acked-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>

Re: [PATCH] can: janz-ican3: initialize dlc variable

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by Marc Kleine-Budde <mkl@pengutronix.de>:

On Sat,  8 Jan 2022 06:33:19 -0800 you wrote:
> From: Tom Rix <trix@redhat.com>
> 
> Clang static analysis reports this problem
> janz-ican3.c:1311:2: warning: Undefined or garbage value returned to caller
>         return dlc;
>         ^~~~~~~~~~
> 
> [...]

Here is the summary with links:
  - can: janz-ican3: initialize dlc variable
    https://git.kernel.org/netdev/net-next/c/c57979256283

You are awesome, thank you!
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