Re: [PATCH v2] serial: samsung: fix buffer size for clk_name

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Wed, Feb 01, 2023 at 05:44:57AM +0300, Alexey V. Vissarionov wrote:
> serial: samsung: fix buffer size for clk_name
> 
> Although very unlikely, the 'clk_num' value may be as big as
> 2**32 - 1 (uint32_max), so the buffer should have enough
> space for storing "clk_uart_baud4294967295\0".
> Also, the numbers in clk_name are expected to be unsigned.
> 
> Found by ALT Linux Team (altlinux.org) and Linux Verification
> Center (linuxtesting.org) using SVACE.
> 
> Signed-off-by: Alexey V. Vissarionov <gremlin@altlinux.org>
> Fixes: 5f5a7a5578c5 ("serial: samsung: switch to clkdev based clock lookup")
> 
> ---
> 
> On 2023-01-19 15:52:38 +0100, Greg Kroah-Hartman wrote:
> 
>  >> Fixes: 5f5a7a5578c58852 ("serial: samsung: switch to clkdev
>  >> based clock lookup")
>  > Please fix your scripts to use the proper number of SHA1 digits
>  > in a Fixes: line as the documentation asks for.
> 
> Done. Also added the comment to the source regarding the buffer size.
> 
> 
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index 0fce856434dafd80..2c701dc7c6a37191 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -1407,7 +1407,7 @@ static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
>   *
>   */
>  
> -#define MAX_CLK_NAME_LENGTH 15
> +#define MAX_CLK_NAME_LENGTH 24		/* "clk_uart_baud4294967295\0" */
>  
>  static inline int s3c24xx_serial_getsource(struct uart_port *port)
>  {
> @@ -1457,7 +1457,7 @@ static unsigned int s3c24xx_serial_getclk(struct s3c24xx_uart_port *ourport,
>  			!(ourport->cfg->clk_sel & (1 << cnt)))
>  			continue;
>  
> -		sprintf(clkname, "clk_uart_baud%d", cnt);
> +		sprintf(clkname, "clk_uart_baud%u", cnt);

So you bump the size of the buffer and continue to use an "unsafe" call
that could overflow the buffer?  Is this a plan to submit a series of
patches all "fixing" something based on the last change?  :)

As Krzysztof said, this whole thing is not needed at all.  Please fix
your tool to generate valid changes.

thanks,

greg k-h

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