Re: [PULL 35/68] hw/mem/cxl_type3: Fix missing ERRP_GUARD() in ct3_realize()

[Zhao Liu]

Hi Michael,

Thanks a lot and aslo this one, I forgot to update the status :/,
this patch has been merged (commit 294cbbf1753e, "hw/mem/cxl_type3:
Fix missing ERRP_GUARD() in ct3_realize()"). Sorry to make you
repeat the merge.

Best Regards,
Zhao

On Tue, Mar 12, 2024 at 06:27:19PM -0400, Michael S. Tsirkin wrote:
> Date: Tue, 12 Mar 2024 18:27:19 -0400
> From: "Michael S. Tsirkin" <mst@redhat.com>
> Subject: [PULL 35/68] hw/mem/cxl_type3: Fix missing ERRP_GUARD() in
>  ct3_realize()
> X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1
> 
> From: Zhao Liu <zhao1.liu@intel.com>
> 
> As the comment in qapi/error, dereferencing @errp requires
> ERRP_GUARD():
> 
> * = Why, when and how to use ERRP_GUARD() =
> *
> * Without ERRP_GUARD(), use of the @errp parameter is restricted:
> * - It must not be dereferenced, because it may be null.
> ...
> * ERRP_GUARD() lifts these restrictions.
> *
> * To use ERRP_GUARD(), add it right at the beginning of the function.
> * @errp can then be used without worrying about the argument being
> * NULL or &error_fatal.
> *
> * Using it when it's not needed is safe, but please avoid cluttering
> * the source with useless code.
> 
> But in ct3_realize(), @errp is dereferenced without ERRP_GUARD():
> 
> cxl_doe_cdat_init(cxl_cstate, errp);
> if (*errp) {
>     goto err_free_special_ops;
> }
> 
> Here we check *errp, because cxl_doe_cdat_init() returns void. And
> ct3_realize() - as a PCIDeviceClass.realize() method - doesn't get the
> NULL @errp parameter, it hasn't triggered the bug that dereferencing
> the NULL @errp.
> 
> To follow the requirement of @errp, add missing ERRP_GUARD() in
> ct3_realize().
> 
> Suggested-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> Reviewed-by: Markus Armbruster <armbru@redhat.com>
> Message-Id: <20240223085653.1255438-4-zhao1.liu@linux.intel.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>  hw/mem/cxl_type3.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> index b679dfae1c..b0a7e9f11b 100644
> --- a/hw/mem/cxl_type3.c
> +++ b/hw/mem/cxl_type3.c
> @@ -645,6 +645,7 @@ static DOEProtocol doe_cdat_prot[] = {
>  
>  static void ct3_realize(PCIDevice *pci_dev, Error **errp)
>  {
> +    ERRP_GUARD();
>      CXLType3Dev *ct3d = CXL_TYPE3(pci_dev);
>      CXLComponentState *cxl_cstate = &ct3d->cxl_cstate;
>      ComponentRegisters *regs = &cxl_cstate->crb;
> -- 
> MST
>