Re: [PATCH v2 06/14] powerpc/pseries/ras: FWNMI_VALID off by one

[Christophe Leroy <christophe.leroy@c-s.fr>]

Le 03/04/2020 à 15:26, Nicholas Piggin a écrit :
> This was discovered developing qemu fwnmi sreset support. This
> off-by-one bug means the last 16 bytes of the rtas area can not
> be used for a 16 byte save area.
> 
> It's not a serious bug, and QEMU implementation has to retain a
> workaround for old kernels, but it's good to tighten it.
> 
> Acked-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>   arch/powerpc/platforms/pseries/ras.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
> index c74d5e740922..9a37bda47468 100644
> --- a/arch/powerpc/platforms/pseries/ras.c
> +++ b/arch/powerpc/platforms/pseries/ras.c
> @@ -395,10 +395,11 @@ static irqreturn_t ras_error_interrupt(int irq, void *dev_id)
>   /*
>    * Some versions of FWNMI place the buffer inside the 4kB page starting at
>    * 0x7000. Other versions place it inside the rtas buffer. We check both.
> + * Minimum size of the buffer is 16 bytes.
>    */
>   #define VALID_FWNMI_BUFFER(A) \
> -	((((A) >= 0x7000) && ((A) < 0x7ff0)) || \
> -	(((A) >= rtas.base) && ((A) < (rtas.base + rtas.size - 16))))
> +	((((A) >= 0x7000) && ((A) <= 0x8000 - 16)) || \
> +	(((A) >= rtas.base) && ((A) <= (rtas.base + rtas.size - 16))))

Why not just change < to <= and leave the 0x7ff0 ?

>   
>   static inline struct rtas_error_log *fwnmi_get_errlog(void)
>   {
> 

Christophe