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

[Alexander Bulekov]

On 221024 1742, 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>

Reviewed-by: Alexander Bulekov <alxndr@bu.edu>

> Signed-off-by: Christian A. Ehrhardt <lk@c--e.de>
> ---
>  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;
> -- 
> 2.34.1
> 
>