Re: [PATCH] perf/x86/intel/uncore: Avoid null dereferences (uncore_extra_pci_dev)

[Liang, Kan]

On 4/15/2021 5:19 PM, Liang, Kan wrote:
> Hi Steve,
>
> On 4/15/2021 4:37 PM, Steve Wahl wrote:
> > If an uncore has no pci_init routine, or that routine fails,
> > uncore_pci_init is not called, and memory is not allocated for
> > uncore_extra_pci_dev.
> >
> > So check to make sure uncore_extra_pci_dev is not NULL before use.
>
> I think more after yesterday's discussion. There may be a better 
> solution than this.
>
> Actually, we don't have to probe all the PCU devices and stores them 
> into the uncore_extra_pci_dev for the cpu_init().
> We just need to pick up the first PCU device and check the existence of 
> the SBOX once.
>
> I will send out a patch shortly.

Here is the patch I mentioned.

https://lore.kernel.org/lkml/1618521764-100923-1-git-send-email-kan.liang@xxxxxxxxxxxxxxx

Thanks,
Kan

> > And fix the case that led us to discover the null derefs; don't fail
> > snbep_pci2phy_map_init if BIOS doesn't supply pcibus_to_node
> > information.
> >
> > Fixes: 9a7832ce3d92 ("perf/x86/intel/uncore: With > 8 nodes, get pci 
> > bus die id from NUMA info")
>
> In theory, the pci_read_config_dword() may fails as well. It has 
> possible that the issue can still be observed before the "> 8 nodes" patch.
>
> I think the fixes should be 5306c31c5733 ("perf/x86/uncore/hsw-ep: 
> Handle systems with only two SBOXes")
>
> Thanks,
> Kan
>
> > Signed-off-by: Steve Wahl <steve.wahl@xxxxxxx>
> > ---
> >   arch/x86/events/intel/uncore_snbep.c | 10 +++++++---
> >   1 file changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/events/intel/uncore_snbep.c 
> > b/arch/x86/events/intel/uncore_snbep.c
> > index b79951d0707c..14c24356a2fa 100644
> > --- a/arch/x86/events/intel/uncore_snbep.c
> > +++ b/arch/x86/events/intel/uncore_snbep.c
> > @@ -1373,11 +1373,11 @@ static int snbep_pci2phy_map_init(int devid, 
> > int nodeid_loc, int idmap_loc, bool
> >           /*
> >            * The nodeid and idmap registers only contain enough
> >            * information to handle 8 nodes.  On systems with more
> > -         * than 8 nodes, we need to rely on NUMA information,
> > +         * than 8 nodes, if available we rely on NUMA information,
> >            * filled in from BIOS supplied information, to determine
> >            * the topology.
> >            */
> > -        if (nr_node_ids <= 8) {
> > +        if ((nr_node_ids <= 8) || (pcibus_to_node(ubox_dev->bus) == 
> > -1)) {
> >               /* get the Node ID of the local register */
> >               err = pci_read_config_dword(ubox_dev, nodeid_loc, &config);
> >               if (err)
> > @@ -2865,7 +2865,9 @@ void hswep_uncore_cpu_init(void)
> >           hswep_uncore_cbox.num_boxes = boot_cpu_data.x86_max_cores;
> >       /* Detect 6-8 core systems with only two SBOXes */
> > -    if (uncore_extra_pci_dev[pkg].dev[HSWEP_PCI_PCU_3]) {
> > +    if (!uncore_extra_pci_dev)
> > +        hswep_uncore_sbox.num_boxes = 2;
> > +    else if (uncore_extra_pci_dev[pkg].dev[HSWEP_PCI_PCU_3]) {
> >           u32 capid4;
> >           
> > pci_read_config_dword(uncore_extra_pci_dev[pkg].dev[HSWEP_PCI_PCU_3],
> > @@ -3243,6 +3245,8 @@ void bdx_uncore_cpu_init(void)
> >       if (boot_cpu_data.x86_model == 86) {
> >           uncore_msr_uncores[BDX_MSR_UNCORE_SBOX] = NULL;
> >       /* Detect systems with no SBOXes */
> > +    } else if (!uncore_extra_pci_dev) {
> > +        bdx_msr_uncores[BDX_MSR_UNCORE_SBOX] = NULL;
> >       } else if (uncore_extra_pci_dev[pkg].dev[HSWEP_PCI_PCU_3]) {
> >           struct pci_dev *pdev;
> >           u32 capid4;