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[PATCH 5/6] hw/pci-bridge/cxl_upstream: Fix missing ERRP_GUARD() in cxl_usp_realize()

Zhao Liu posted 6 patches 9 months, 1 week ago
Maintainers: Jonathan Cameron <jonathan.cameron@huawei.com>, Fan Ni <fan.ni@samsung.com>, Laurent Vivier <laurent@vivier.eu>, Alistair Francis <alistair@alistair23.me>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, Peter Maydell <peter.maydell@linaro.org>, "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Alex Williamson <alex.williamson@redhat.com>, "Cédric Le Goater" <clg@redhat.com>
[PATCH 5/6] hw/pci-bridge/cxl_upstream: Fix missing ERRP_GUARD() in cxl_usp_realize()
Posted by Zhao Liu 9 months, 1 week ago 
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.
* - 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 <armbru@redhat.com>
Signed-off-by: Zhao Liu <zhao1.liu@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;
-- 
2.34.1
Re: [PATCH 5/6] hw/pci-bridge/cxl_upstream: Fix missing ERRP_GUARD() in cxl_usp_realize()
Posted by Markus Armbruster 9 months, 1 week ago 
Zhao Liu <zhao1.liu@linux.intel.com> writes:

> 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.
> * - 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 <armbru@redhat.com>
> Signed-off-by: Zhao Liu <zhao1.liu@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 <armbru@redhat.com>
Re: [PATCH 5/6] hw/pci-bridge/cxl_upstream: Fix missing ERRP_GUARD() in cxl_usp_realize()
Posted by Zhao Liu 9 months, 1 week ago 
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 <armbru@redhat.com>
> Subject: Re: [PATCH 5/6] hw/pci-bridge/cxl_upstream: Fix missing
>  ERRP_GUARD() in cxl_usp_realize()
> 
> Zhao Liu <zhao1.liu@linux.intel.com> writes:
> 
> > 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.
> > * - 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 <armbru@redhat.com>
> > Signed-off-by: Zhao Liu <zhao1.liu@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 <armbru@redhat.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
Re: [PATCH 5/6] hw/pci-bridge/cxl_upstream: Fix missing ERRP_GUARD() in cxl_usp_realize()
Posted by Jonathan Cameron via 9 months ago 
On Wed, 21 Feb 2024 23:09:49 +0800
Zhao Liu <zhao1.liu@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 <armbru@redhat.com>
> > Subject: Re: [PATCH 5/6] hw/pci-bridge/cxl_upstream: Fix missing
> >  ERRP_GUARD() in cxl_usp_realize()
> > 
> > Zhao Liu <zhao1.liu@linux.intel.com> writes:
> >   
> > > 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.
> > > * - 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 <armbru@redhat.com>
> > > Signed-off-by: Zhao Liu <zhao1.liu@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 <armbru@redhat.com>
> >  
Acked-by: Jonathan Cameron <Jonathan.Cameron@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
>

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