[U-Boot] [PATCH v3] arm: socfpga: mailbox: Fix off-by-one error on command length checking

[Marek Vasut]

On 4/19/19 8:17 AM, Ley Foon Tan wrote:
> A mailbox command contains 1-DWORD header + arguments. The "len" variable
> only contains the length of the arguments, but not the 1-DWORD header.
> Include the length of header when checking the ring buffer space to
> prevent off-by-one error.

How long is a DWORD ? Windows API (which we have nothing to do with)
defines that as 32bit type, "typedef unsigned long DWORD;", see [1].
But the patch below fixes an off-by-one error , not off by four error ?

[1]
https://docs.microsoft.com/en-us/windows/desktop/winprog/windows-data-types

> Signed-off-by: Ley Foon Tan <ley.foon.tan at intel.com>
> Signed-off-by: Chee Hong Ang <chee.hong.ang at intel.com>
> ---
> v2->v3:
> - Update commit description.
> ---
>  arch/arm/mach-socfpga/mailbox_s10.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-socfpga/mailbox_s10.c b/arch/arm/mach-socfpga/mailbox_s10.c
> index 3c33223936..8363c93e90 100644
> --- a/arch/arm/mach-socfpga/mailbox_s10.c
> +++ b/arch/arm/mach-socfpga/mailbox_s10.c
> @@ -59,7 +59,7 @@ static __always_inline int mbox_fill_cmd_circular_buff(u32 header, u32 len,
>  	 */
>  	if (((cin + 1) % MBOX_CMD_BUFFER_SIZE) == cout ||
>  	    ((MBOX_CMD_BUFFER_SIZE - cin + cout - 1) %
> -	     MBOX_CMD_BUFFER_SIZE) < len)
> +	     MBOX_CMD_BUFFER_SIZE) < (len + 1))
>  		return -ENOMEM;
>  
>  	/* write header to circular buffer */
> 


-- 
Best regards,
Marek Vasut