Re: [PATCH v2] hw/acpi/erst.c: Fix memory handling issues

[Eric DeVolder]

On 10/24/22 10:42, Christian A. Ehrhardt wrote:
> - Fix memset argument order: The second argument is
>    the value, the length goes last.
> - Fix an integer overflow reported by Alexander Bulekov.
>
> Both issues allow the guest to overrun the host buffer
> allocated for the ERST memory device.
>
> Cc: Eric DeVolder <eric.devolder@oracle.com
> Cc: Alexander Bulekov <alxndr@bu.edu>
> Cc: qemu-stable@nongnu.org
> Fixes: f7e26ffa590 ("ACPI ERST: support for ACPI ERST feature")
> Tested-by: Alexander Bulekov <alxndr@bu.edu>
> Signed-off-by: Christian A. Ehrhardt <lk@c--e.de>

Reviewed-by: Eric DeVolder <eric.devolder@oracle.com>

Thanks Christian!
eric

> ---
>   hw/acpi/erst.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/hw/acpi/erst.c b/hw/acpi/erst.c
> index df856b2669..aefcc03ad6 100644
> --- a/hw/acpi/erst.c
> +++ b/hw/acpi/erst.c
> @@ -635,7 +635,7 @@ static unsigned read_erst_record(ERSTDeviceState *s)
>           if (record_length < UEFI_CPER_RECORD_MIN_SIZE) {
>               rc = STATUS_FAILED;
>           }
> -        if ((s->record_offset + record_length) > exchange_length) {
> +        if (record_length > exchange_length - s->record_offset) {
>               rc = STATUS_FAILED;
>           }
>           /* If all is ok, copy the record to the exchange buffer */
> @@ -684,7 +684,7 @@ static unsigned write_erst_record(ERSTDeviceState *s)
>       if (record_length < UEFI_CPER_RECORD_MIN_SIZE) {
>           return STATUS_FAILED;
>       }
> -    if ((s->record_offset + record_length) > exchange_length) {
> +    if (record_length > exchange_length - s->record_offset) {
>           return STATUS_FAILED;
>       }
>   
> @@ -716,7 +716,7 @@ static unsigned write_erst_record(ERSTDeviceState *s)
>       if (nvram) {
>           /* Write the record into the slot */
>           memcpy(nvram, exchange, record_length);
> -        memset(nvram + record_length, exchange_length - record_length, 0xFF);
> +        memset(nvram + record_length, 0xFF, exchange_length - record_length);
>           /* If a new record, increment the record_count */
>           if (!record_found) {
>               uint32_t record_count;