Re: [PATCH-for-5.1] hw/misc/aspeed_sdmc: Fix incorrect memory size

[Cédric Le Goater]

On 7/20/20 11:58 AM, Philippe Mathieu-Daudé wrote:
> The SDRAM Memory Controller has a 32-bit address bus, thus
> supports up to 4 GiB of DRAM. There is a signed to unsigned
> conversion error with the AST2600 maximum memory size:
> 
>   (uint64_t)(2048 << 20) = (uint64_t)(-2147483648)
>                          = 0xffffffff40000000
>                          = 16 EiB - 2 GiB
> 
> Fix by using the IEC suffixes which are usually safer, and add
> a check to verify the memory is valid. This would have catched
> this bug:
> 
>     Unexpected error in aspeed_sdmc_realize() at hw/misc/aspeed_sdmc.c:261:
>     qemu-system-arm: Invalid RAM size 16 EiB

Indeed :/

> 
> Fixes: 1550d72679 ("aspeed/sdmc: Add AST2600 support")
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  hw/misc/aspeed_sdmc.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/misc/aspeed_sdmc.c b/hw/misc/aspeed_sdmc.c
> index 0737d8de81..76dd7e6a20 100644
> --- a/hw/misc/aspeed_sdmc.c
> +++ b/hw/misc/aspeed_sdmc.c
> @@ -256,6 +256,12 @@ static void aspeed_sdmc_realize(DeviceState *dev, Error 
> **errp)
>      AspeedSDMCClass *asc = ASPEED_SDMC_GET_CLASS(s);
>  
>      s->max_ram_size = asc->max_ram_size;
> +    if (s->max_ram_size >= 4 * GiB) {
> +        char *szstr = size_to_str(s->max_ram_size);
> +        error_setg(errp, "Invalid RAM size %s", szstr);
> +        g_free(szstr);
> +        return;
> +    }
>

I would put an assert() since the max RAM size is not user configurable. 

C.

>      memory_region_init_io(&s->iomem, OBJECT(s), &aspeed_sdmc_ops, s,
>                            TYPE_ASPEED_SDMC, 0x1000);
> @@ -341,7 +347,7 @@ static void aspeed_2400_sdmc_class_init(ObjectClass 
> *klass, void *data)
>      AspeedSDMCClass *asc = ASPEED_SDMC_CLASS(klass);
>  
>      dc->desc = "ASPEED 2400 SDRAM Memory Controller";
> -    asc->max_ram_size = 512 << 20;
> +    asc->max_ram_size = 512 * MiB;
>      asc->compute_conf = aspeed_2400_sdmc_compute_conf;
>      asc->write = aspeed_2400_sdmc_write;
>      asc->valid_ram_sizes = aspeed_2400_ram_sizes;
> @@ -408,7 +414,7 @@ static void aspeed_2500_sdmc_class_init(ObjectClass 
> *klass, void *data)
>      AspeedSDMCClass *asc = ASPEED_SDMC_CLASS(klass);
>  
>      dc->desc = "ASPEED 2500 SDRAM Memory Controller";
> -    asc->max_ram_size = 1024 << 20;
> +    asc->max_ram_size = 1 * GiB;
>      asc->compute_conf = aspeed_2500_sdmc_compute_conf;
>      asc->write = aspeed_2500_sdmc_write;
>      asc->valid_ram_sizes = aspeed_2500_ram_sizes;
> @@ -485,7 +491,7 @@ static void aspeed_2600_sdmc_class_init(ObjectClass 
> *klass, void *data)
>      AspeedSDMCClass *asc = ASPEED_SDMC_CLASS(klass);
>  
>      dc->desc = "ASPEED 2600 SDRAM Memory Controller";
> -    asc->max_ram_size = 2048 << 20;
> +    asc->max_ram_size = 2 * GiB;
>      asc->compute_conf = aspeed_2600_sdmc_compute_conf;
>      asc->write = aspeed_2600_sdmc_write;
>      asc->valid_ram_sizes = aspeed_2600_ram_sizes;
>