Re: [PATCH v3] Add missing initialization for g_autofree variables

[Matthew Rosato]

On 3/15/21 6:42 AM, Cornelia Huck wrote:
> On Mon, 15 Mar 2021 11:13:52 +0100
> mrezanin@redhat.com wrote:
>
> > From: Miroslav Rezanina <mrezanin@redhat.com>
> >
> > When declaring g_autofree variable without inicialization, compiler
> > will raise "may be used uninitialized in this function" warning due
> > to automatic free handling.
> >
> > This is mentioned in docs/devel/style.rst (quote from section
> > "Automatic memory deallocation"):
> >
> >    * Variables declared with g_auto* MUST always be initialized,
> >      otherwise the cleanup function will use uninitialized stack memory
> >
> > Add inicialization for these declarations to prevent the warning and
> > comply with coding style.
>
> Fixes: cd7498d07fbb ("s390x/pci: Add routine to get the vfio dma available 
> count")
> Fixes: 1e7552ff5c34 ("s390x/pci: get zPCI function info from host")
>
> I can fix the spelling mistakes pointed out by Phil while applying, and
> also add an 's390x/pci' prefix.
>
> Would not mind a quick test run from someone with the hardware.

Sure, I took this for a spin (ConnectX-3 VF via vfio-pci) and made sure 
both code paths were being driven without issue.  Code looks fine as well.

Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>

> > Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
> >
> > ---
> > * v3:
> >    -- allocate in s390_pci_update_dma_avail instead of NULL init
> >
> > * v2:
> >    -- Removed fixes in hw/remote/memory.c and hw/remote/proxy.c
> >       fixed by patch sent by Zenghui Yu (multi-process: Initialize
> >       variables declared with g_auto*)
> > ---
> >   hw/s390x/s390-pci-vfio.c | 9 +++------
> >   1 file changed, 3 insertions(+), 6 deletions(-)
> >
> > diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
> > index ead4f222d5..2a153fa8c9 100644
> > --- a/hw/s390x/s390-pci-vfio.c
> > +++ b/hw/s390x/s390-pci-vfio.c
> > @@ -29,14 +29,11 @@
> >    */
> >   bool s390_pci_update_dma_avail(int fd, unsigned int *avail)
> >   {
> > -    g_autofree struct vfio_iommu_type1_info *info;
> > -    uint32_t argsz;
> > +    uint32_t argsz = sizeof(struct vfio_iommu_type1_info);
> > +    g_autofree struct vfio_iommu_type1_info *info = g_malloc0(argsz);
> >   
> >       assert(avail);
> >   
> > -    argsz = sizeof(struct vfio_iommu_type1_info);
> > -    info = g_malloc0(argsz);
> > -
> >       /*
> >        * If the specified argsz is not large enough to contain all capabilities
> >        * it will be updated upon return from the ioctl.  Retry until we have
> > @@ -230,7 +227,7 @@ static void s390_pci_read_pfip(S390PCIBusDevice *pbdev,
> >    */
> >   void s390_pci_get_clp_info(S390PCIBusDevice *pbdev)
> >   {
> > -    g_autofree struct vfio_device_info *info;
> > +    g_autofree struct vfio_device_info *info = NULL;
> >       VFIOPCIDevice *vfio_pci;
> >       uint32_t argsz;
> >       int fd;