linux-kernel - [PATCH] perf/x86/intel/uncore: Avoid null dereferences (uncore_extra_pci

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Date:   Thu, 15 Apr 2021 15:37:20 -0500
From:   Steve Wahl <steve.wahl@....com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Steve Wahl <steve.wahl@....com>, linux-kernel@...r.kernel.org
Subject: [PATCH] perf/x86/intel/uncore: Avoid null dereferences (uncore_extra_pci_dev)

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.

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")

Signed-off-by: Steve Wahl <steve.wahl@....com>
---
 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;
-- 
2.26.2