Re: [PULL v2 18/24] ACPI ERST: support for ACPI ERST feature

[Peter Maydell]

On Sun, 6 Feb 2022 at 09:38, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> From: Eric DeVolder <eric.devolder@oracle.com>
>
> This implements a PCI device for ACPI ERST. This implements the
> non-NVRAM "mode" of operation for ERST as it is supported by
> Linux and Windows.
>
> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
> Reviewed-by: Ani Sinha <ani@anisinha.ca>
> Message-Id: <1643402289-22216-6-git-send-email-eric.devolder@oracle.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---

Hi; Coverity points out a bug in this function (CID 1487125):

> +static void check_erst_backend_storage(ERSTDeviceState *s, Error **errp)
> +{
> +    ERSTStorageHeader *header;
> +    uint32_t record_size;
> +
> +    header = memory_region_get_ram_ptr(s->hostmem_mr);
> +    s->header = header;
> +
> +    /* Ensure pointer to header is 64-bit aligned */
> +    g_assert(QEMU_PTR_IS_ALIGNED(header, sizeof(uint64_t)));
> +
> +    /*
> +     * Check if header is uninitialized; HostMemoryBackend inits to 0
> +     */
> +    if (le64_to_cpu(header->magic) == 0UL) {
> +        make_erst_storage_header(s);
> +    }
> +
> +    /* Validity check record_size */
> +    record_size = le32_to_cpu(header->record_size);
> +    if (!(
> +        (record_size) && /* non zero */
> +        (record_size >= UEFI_CPER_RECORD_MIN_SIZE) &&
> +        (((record_size - 1) & record_size) == 0) && /* is power of 2 */
> +        (record_size >= 4096) /* PAGE_SIZE */
> +        )) {
> +        error_setg(errp, "ERST record_size %u is invalid", record_size);

Here we check that record_size is sensible, including that it is
not zero. But we forget to return early after error_setg(), which means...

> +    }
> +
> +    /* Validity check header */
> +    if (!(
> +        (le64_to_cpu(header->magic) == ERST_STORE_MAGIC) &&
> +        ((le32_to_cpu(header->storage_offset) % record_size) == 0) &&
> +        (le16_to_cpu(header->version) == 0x0100) &&
> +        (le16_to_cpu(header->reserved) == 0)
> +        )) {
> +        error_setg(errp, "ERST backend storage header is invalid");
> +    }
> +
> +    /* Check storage_size against record_size */
> +    if (((s->storage_size % record_size) != 0) ||

...that we fall through to here, where we will divide by zero if
record_size is 0.

> +         (record_size > s->storage_size)) {
> +        error_setg(errp, "ACPI ERST requires storage size be multiple of "
> +            "record size (%uKiB)", record_size);
> +    }
> +
> +    /* Compute offset of first and last record storage slot */
> +    s->first_record_index = le32_to_cpu(header->storage_offset)
> +        / record_size;
> +    s->last_record_index = (s->storage_size / record_size);
> +}
> +

The fix is probably simply to add return statements after each error_setg()
in the function.

thanks
-- PMM