linux-kernel - [PATCH] perf/x86/intel/uncore: Fix NULL pointer dereference issue in upi_fill

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Message-Id: <20231115151327.1874060-1-alexander.antonov@linux.intel.com>
Date:   Wed, 15 Nov 2023 07:13:27 -0800
From:   alexander.antonov@...ux.intel.com
To:     peterz@...radead.org, linux-kernel@...r.kernel.org
Cc:     kyle.meyer@....com, kan.liang@...ux.intel.com,
        alexey.v.bayduraev@...ux.intel.com,
        alexander.antonov@...ux.intel.com
Subject: [PATCH] perf/x86/intel/uncore: Fix NULL pointer dereference issue in upi_fill_topology()

From: Alexander Antonov <alexander.antonov@...ux.intel.com>

The NULL dereference happens inside upi_fill_topology() procedure in
case of disabling one of the sockets on the system.

For example, if you disable the 2nd socket on a 4-socket system then
uncore_max_dies() returns 3 and inside pmu_alloc_topology() memory will
be allocated only for 3 sockets and stored in type->topology.
In discover_upi_topology() memory is accessed by socket id from CPUNODEID
registers which contain physical ids (from 0 to 3) and on the line:

    upi = &type->topology[nid][idx];

out-of-bound access will happen and the 'upi' pointer will be passed to
upi_fill_topology() where it will be dereferenced.

To avoid this issue update the code to convert physical socket id to
logical socket id in discover_upi_topology() before accessing memory.

Fixes: f680b6e6062e ("perf/x86/intel/uncore: Enable UPI topology discovery for Icelake Server")
Reported-by: Kyle Meyer <kyle.meyer@....com>
Tested-by: Kyle Meyer <kyle.meyer@....com>
Signed-off-by: Alexander Antonov <alexander.antonov@...ux.intel.com>
---
 arch/x86/events/intel/uncore_snbep.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c
index 8250f0f59c2b..49bc27ab26ad 100644
--- a/arch/x86/events/intel/uncore_snbep.c
+++ b/arch/x86/events/intel/uncore_snbep.c
@@ -5596,7 +5596,7 @@ static int discover_upi_topology(struct intel_uncore_type *type, int ubox_did, i
 	struct pci_dev *ubox = NULL;
 	struct pci_dev *dev = NULL;
 	u32 nid, gid;
-	int i, idx, ret = -EPERM;
+	int i, idx, lgc_pkg, ret = -EPERM;
 	struct intel_uncore_topology *upi;
 	unsigned int devfn;
 
@@ -5614,8 +5614,13 @@ static int discover_upi_topology(struct intel_uncore_type *type, int ubox_did, i
 		for (i = 0; i < 8; i++) {
 			if (nid != GIDNIDMAP(gid, i))
 				continue;
+			lgc_pkg = topology_phys_to_logical_pkg(i);
+			if (lgc_pkg < 0) {
+				ret = -EPERM;
+				goto err;
+			}
 			for (idx = 0; idx < type->num_boxes; idx++) {
-				upi = &type->topology[nid][idx];
+				upi = &type->topology[lgc_pkg][idx];
 				devfn = PCI_DEVFN(dev_link0 + idx, ICX_UPI_REGS_ADDR_FUNCTION);
 				dev = pci_get_domain_bus_and_slot(pci_domain_nr(ubox->bus),
 								  ubox->bus->number,
@@ -5626,6 +5631,7 @@ static int discover_upi_topology(struct intel_uncore_type *type, int ubox_did, i
 						goto err;
 				}
 			}
+			break;
 		}
 	}
 err:

base-commit: 9bacdd8996c77c42ca004440be610692275ff9d0
-- 
2.25.1