Re: [PATCH] perf/arm-cmn: Reject unsupported hardware configurations

So far we've been fairly lax about accepting both unknown CMN models
(at least with a warning), and unknown revisions of those which we
do know, as although things do frequently change between releases,
typically enough remains the same to be somewhat useful for at least
some basic bringup checks. However, we also make assumptions of the
maximum supported sizes and numbers of things in various places, and
there's no guarantee that something new might not be bigger and lead
to nasty array overflows. Make sure we only try to run on things that
actually match our assumptions and so will not risk memory corruption.

Cc: stable@vger.kernel.org
Fixes: 7819e05a0dce ("perf/arm-cmn: Revamp model detection")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
drivers/perf/arm-cmn.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index 2903e01f951f..24fec53ceccc 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c

@@ -2422,6 +2422,15 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)

			arm_cmn_init_node_info(cmn, reg & CMN_CHILD_NODE_ADDR, dn);
			dn->portid_bits = xp->portid_bits;
			dn->deviceid_bits = xp->deviceid_bits;
+			/*
+			 * Logical IDs are assigned from 0 per node type, so as
+			 * soon as we one bigger than expected, we can assume

+			 * there are more than we can cope with.
+			 */
+			if (dn->logid > CMN_MAX_NODES_PER_EVENT) {
+				dev_err(cmn->dev, "Invalid node number: %d\n", dn->logid);
+				return -ENODEV;
+			}

			switch (dn->type) {
			case CMN_TYPE_DTC:

@@ -2499,6 +2508,10 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)

		cmn->mesh_x = cmn->num_xps;
	cmn->mesh_y = cmn->num_xps / cmn->mesh_x;

+	if (max(cmn->mesh_x, cmn->mesh_y) > CMN_MAX_DIMENSION) {
+		dev_err(cmn->dev, "Invalid mesh size: %dx%d\n", cmn->mesh_x, cmn->mesh_y);
+		return -ENODEV;
+	}
	/* 1x1 config plays havoc with XP event encodings */
	if (cmn->num_xps == 1)
		dev_warn(cmn->dev, "1x1 config not fully supported, translate XP events manually\n");
-- 
2.39.2.101.g768bb238c484.dirty