linux-hardening - [PATCH 5/5] slub: Don't read nr_slabs and total

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Date:   Thu, 13 Apr 2023 22:34:52 +0800
From:   sxwjean@...com
To:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org, vbabka@...e.cz,
        roman.gushchin@...ux.dev, 42.hyeyoo@...il.com,
        keescook@...omium.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org,
        Xiongwei Song <xiongwei.song@...driver.com>
Subject: [PATCH 5/5] slub: Don't read nr_slabs and total_objects directly

From: Xiongwei Song <xiongwei.song@...driver.com>

We have node_nr_slabs() to read nr_slabs, node_nr_objs() to read
total_objects in a kmem_cache_node, so no need to access the two
members directly.

Signed-off-by: Xiongwei Song <xiongwei.song@...driver.com>
---
 mm/slub.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 33b4fec6bc7a..2c3af399d9d6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5157,9 +5157,9 @@ static int validate_slab_node(struct kmem_cache *s,
 		validate_slab(s, slab, obj_map);
 		count++;
 	}
-	if (count != atomic_long_read(&n->nr_slabs)) {
+	if (count != node_nr_slabs(n)) {
 		pr_err("SLUB: %s %ld slabs counted but counter=%ld\n",
-		       s->name, count, atomic_long_read(&n->nr_slabs));
+		       s->name, count, node_nr_slabs(n));
 		slab_add_kunit_errors();
 	}
 
@@ -5443,12 +5443,11 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
 		for_each_kmem_cache_node(s, node, n) {
 
 			if (flags & SO_TOTAL)
-				x = atomic_long_read(&n->total_objects);
+				x = node_nr_objs(n);
 			else if (flags & SO_OBJECTS)
-				x = atomic_long_read(&n->total_objects) -
-					count_partial(n, count_free);
+				x = node_nr_objs(n) - count_partial(n, count_free);
 			else
-				x = atomic_long_read(&n->nr_slabs);
+				x = node_nr_slabs(n);
 			total += x;
 			nodes[node] += x;
 		}
@@ -6387,7 +6386,7 @@ static int slab_debug_trace_open(struct inode *inode, struct file *filep)
 		unsigned long flags;
 		struct slab *slab;
 
-		if (!atomic_long_read(&n->nr_slabs))
+		if (!node_nr_slabs(n))
 			continue;
 
 		spin_lock_irqsave(&n->list_lock, flags);
-- 
2.30.2