linux-kernel - Re: [PATCH] serial: sh-sci: fix uninitialized variable warning

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Date:   Fri, 19 Jun 2020 20:38:18 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Charles <18oliveira.charles@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, rodrigosiqueiramelo@...il.com
Subject: Re: [PATCH] serial: sh-sci: fix uninitialized variable warning

On Thu, Jun 13, 2019 at 03:08:24PM -0300, Charles wrote:
> Avoid following compiler warning on uninitialized variable
> 
> In file included from ./include/linux/rwsem.h:16:0,
>                  from ./include/linux/notifier.h:15,
>                  from ./include/linux/clk.h:17,
>                  from drivers/tty/serial/sh-sci.c:24:
> drivers/tty/serial/sh-sci.c: In function ‘sci_dma_rx_submit’:
> ./include/linux/spinlock.h:288:3: warning: ‘flags’ may be used
> uninitialized in this function [-Wmaybe-uninitialized]
>    _raw_spin_unlock_irqrestore(lock, flags); \
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/tty/serial/sh-sci.c:1353:16: note: ‘flags’ was declared here
>   unsigned long flags;
>                 ^~~~~
> 
> Signed-off-by: Charles Oliveira <18oliveira.charles@...il.com>
> ---
>  drivers/tty/serial/sh-sci.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> index abc705716aa0..a6af73eaec11 100644
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -1350,7 +1350,7 @@ static int sci_dma_rx_submit(struct sci_port *s, bool port_lock_held)
>  {
>  	struct dma_chan *chan = s->chan_rx;
>  	struct uart_port *port = &s->port;
> -	unsigned long flags;
> +	unsigned long uninitialized_var(flags);

akpm made this same change in -mm, and it's not the right
solution[1]. Please just initialize it to 0 if the compiler can't figure
it out. :)

-Kees

[1] https://lore.kernel.org/lkml/20200620033007.1444705-2-keescook@chromium.org/

>  	int i;
>  
>  	for (i = 0; i < 2; i++) {
> -- 
> 2.11.0
> 

-- 
Kees Cook