On Wed, 21 Feb 2024 23:09:49 +0800 Zhao Liu <zhao1....@linux.intel.com> wrote:
> On Wed, Feb 21, 2024 at 12:49:46PM +0100, Markus Armbruster wrote: > > Date: Wed, 21 Feb 2024 12:49:46 +0100 > > From: Markus Armbruster <arm...@redhat.com> > > Subject: Re: [PATCH 5/6] hw/pci-bridge/cxl_upstream: Fix missing > > ERRP_GUARD() in cxl_usp_realize() > > > > Zhao Liu <zhao1....@linux.intel.com> writes: > > > > > From: Zhao Liu <zhao1....@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. > > > * - It should not be passed to error_prepend() or > > > * error_append_hint(), because that doesn't work with &error_fatal. > > > * 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. > > > > > > Currently, since cxl_usp_realize() - as a PCIDeviceClass.realize() > > > method - doesn't get the NULL errp parameter, it doesn't trigger the > > > dereference issue. > > > > > > To follow the requirement of errp, add missing ERRP_GUARD() in > > > cxl_usp_realize()(). > > > > > > Suggested-by: Markus Armbruster <arm...@redhat.com> > > > Signed-off-by: Zhao Liu <zhao1....@intel.com> > > > --- > > > Suggested by credit: > > > Markus: Referred his explanation about ERRP_GUARD(). > > > --- > > > hw/pci-bridge/cxl_upstream.c | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c > > > index e87eb4017713..03d123cca0ef 100644 > > > --- a/hw/pci-bridge/cxl_upstream.c > > > +++ b/hw/pci-bridge/cxl_upstream.c > > > @@ -289,6 +289,7 @@ static void free_default_cdat_table(CDATSubHeader > > > **cdat_table, int num, > > > > > > static void cxl_usp_realize(PCIDevice *d, Error **errp) > > > { > > > + ERRP_GUARD(); > > > PCIEPort *p = PCIE_PORT(d); > > > CXLUpstreamPort *usp = CXL_USP(d); > > > CXLComponentState *cxl_cstate = &usp->cxl_cstate; > > > > The dereference is > > > > cxl_doe_cdat_init(cxl_cstate, errp); > > if (*errp) { > > goto err_cap; > > } > > > > As noted in review of PATCH 3, we check *errp, because > > cxl_doe_cdat_init() returns void. Could be improved to return bool, > > along with its callees ct3_load_cdat() and ct3_build_cdat(), but that's > > a slightly more ambitious cleanup, so > > > > Reviewed-by: Markus Armbruster <arm...@redhat.com> > > Acked-by: Jonathan Cameron <jonathan.came...@huawei.com> > > Thanks! It's a good idea and I can continue to consider such the cleanup > in the follow up. > > Will also add the dereference description in commit message to make > review easier. > > Regards, > Zhao >