linux-kernel - [PATCH] drivers: base: cacheinfo: fix shared_cpu

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Date:   Mon, 19 Dec 2022 10:10:36 +0000
From:   Yong-Xuan Wang <yongxuan.wang@...ive.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Vincent Chen <vincent.chen@...ive.com>,
        Greentime Hu <greentime.hu@...ive.com>,
        Yong-Xuan Wang <yongxuan.wang@...ive.com>
Subject: [PATCH] drivers: base: cacheinfo: fix shared_cpu_map

The cacheinfo sets up the shared_cpu_map by checking whether the caches
with the same index are shared between CPUs. However, this will trigger
slab-out-of-bounds access if the CPUs do not have the same cache hierarchy.
Another problem is the mismatched shared_cpu_map when the shared cache does
not have the same index between CPUs.

CPU0	I	D	L3
index	0	1	2	x
	^	^	^	^
index	0	1	2	3
CPU1	I	D	L2	L3

This patch checks each cache is shared with all caches on other CPUs.

Signed-off-by: Yong-Xuan Wang <yongxuan.wang@...ive.com>
---
 drivers/base/cacheinfo.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index dad296229161..815a1398ea16 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -219,7 +219,7 @@ static int cache_shared_cpu_map_setup(unsigned int cpu)
 {
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
 	struct cacheinfo *this_leaf, *sib_leaf;
-	unsigned int index;
+	unsigned int index, sib_index;
 	int ret = 0;
 
 	if (this_cpu_ci->cpu_map_populated)
@@ -247,8 +247,10 @@ static int cache_shared_cpu_map_setup(unsigned int cpu)
 
 			if (i == cpu || !sib_cpu_ci->info_list)
 				continue;/* skip if itself or no cacheinfo */
-			sib_leaf = sib_cpu_ci->info_list + index;
-			if (cache_leaves_are_shared(this_leaf, sib_leaf)) {
+			for (sib_index = 0; sib_index < cache_leaves(i); sib_index++) {
+				sib_leaf = sib_cpu_ci->info_list + sib_index;
+				if (!cache_leaves_are_shared(this_leaf, sib_leaf))
+					continue;
 				cpumask_set_cpu(cpu, &sib_leaf->shared_cpu_map);
 				cpumask_set_cpu(i, &this_leaf->shared_cpu_map);
 			}
@@ -265,7 +267,7 @@ static void cache_shared_cpu_map_remove(unsigned int cpu)
 {
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
 	struct cacheinfo *this_leaf, *sib_leaf;
-	unsigned int sibling, index;
+	unsigned int sibling, index, sib_index;
 
 	for (index = 0; index < cache_leaves(cpu); index++) {
 		this_leaf = this_cpu_ci->info_list + index;
@@ -279,9 +281,13 @@ static void cache_shared_cpu_map_remove(unsigned int cpu)
 			if (!sib_cpu_ci->info_list)
 				continue;
 
-			sib_leaf = sib_cpu_ci->info_list + index;
-			cpumask_clear_cpu(cpu, &sib_leaf->shared_cpu_map);
-			cpumask_clear_cpu(sibling, &this_leaf->shared_cpu_map);
+			for (sib_index = 0; sib_index < cache_leaves(sibling); sib_index++) {
+				sib_leaf = sib_cpu_ci->info_list + sib_index;
+				if (!cache_leaves_are_shared(this_leaf, sib_leaf))
+					continue;
+				cpumask_clear_cpu(cpu, &sib_leaf->shared_cpu_map);
+				cpumask_clear_cpu(sibling, &this_leaf->shared_cpu_map);
+			}
 		}
 		if (of_have_populated_dt())
 			of_node_put(this_leaf->fw_token);
-- 
2.17.1