Re: [PULL 24/30] spapr_pci: populate ibm,loc-code

[Peter Maydell]

On Tue, 10 Aug 2021 at 05:40, David Gibson <david@gibson.dropbear.id.au> wrote:
>
> On Mon, Aug 09, 2021 at 10:57:00AM +0100, Peter Maydell wrote:
> >
> > Cleanest fix would be to declare 'path' and 'host' as
> >    g_autofree char *path = NULL;
> >    g_autofree char *host = NULL;
> > and then you can remove all the manual g_free(path) and g_free(host) calls.
>
> Thanks for the report.  I've committed the fix (I hope) below to ppc-for-6.1:
>
> From 70ae61b510dc571c407b28c46498cae60e60ca66 Mon Sep 17 00:00:00 2001
> From: David Gibson <david@gibson.dropbear.id.au>
> Date: Tue, 10 Aug 2021 14:28:19 +1000
> Subject: [PATCH] spapr_pci: Fix leak in spapr_phb_vfio_get_loc_code() with
>  g_autofree
>
> This uses g_autofree to simplify logic in spapr_phb_vfio_get_loc_code(),
> in the process fixing a leak in one of the paths.  I'm told this fixes
> Coverity error CID 1460454
>
> Reported-by: Peter Maydell <peter.maydell@linaro.org>
> Fixes: 16b0ea1d852 ("spapr_pci: populate ibm,loc-code")
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  hw/ppc/spapr_pci.c | 17 ++++++-----------
>  1 file changed, 6 insertions(+), 11 deletions(-)
>
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index 7a725855f9..13d806f390 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -782,33 +782,28 @@ static AddressSpace *spapr_pci_dma_iommu(PCIBus *bus, 
> void *opaque, int devfn)
>
>  static char *spapr_phb_vfio_get_loc_code(SpaprPhbState *sphb,  PCIDevice 
> *pdev)
>  {
> -    char *path = NULL, *buf = NULL, *host = NULL;
> +    g_autofree char *path = NULL;
> +    g_autofree char *host = NULL;
> +    char *buf = NULL;
>
>      /* Get the PCI VFIO host id */
>      host = object_property_get_str(OBJECT(pdev), "host", NULL);
>      if (!host) {
> -        goto err_out;
> +        return NULL;
>      }
>
>      /* Construct the path of the file that will give us the DT location */
>      path = g_strdup_printf("/sys/bus/pci/devices/%s/devspec", host);
> -    g_free(host);
>      if (!g_file_get_contents(path, &buf, NULL, NULL)) {
> -        goto err_out;
> +        return NULL;
>      }
> -    g_free(path);
>
>      /* Construct and read from host device tree the loc-code */
>      path = g_strdup_printf("/proc/device-tree%s/ibm,loc-code", buf);
> -    g_free(buf);

This deletion doesn't look right -- 'buf' is not autofree
(and shouldn't be, since we're returning it).

If you want to delete this 'g_free' you need to make the
first g_file_get_contents() use a separate char* variable from
the variable we use to return the eventual result data buffer;
then you can make that new variable be g_autofree.

>      if (!g_file_get_contents(path, &buf, NULL, NULL)) {
> -        goto err_out;
> +        return NULL;
>      }
>      return buf;
> -
> -err_out:
> -    g_free(path);
> -    return NULL;
>  }

thanks
-- PMM