linux-kernel - [PATCH] mm: fix a possible null pointer dereference in setup_zone

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Message-Id: <20241107113447.402194-1-chenqiuji666@gmail.com>
Date: Thu,  7 Nov 2024 19:34:47 +0800
From: Qiu-ji Chen <chenqiuji666@...il.com>
To: akpm@...ux-foundation.org
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	baijiaju1990@...il.com,
	Qiu-ji Chen <chenqiuji666@...il.com>,
	stable@...r.kernel.org
Subject: [PATCH] mm: fix a possible null pointer dereference in setup_zone_pageset()

The function call alloc_percpu() returns a pointer to the memory address,
but it hasn't been checked. Our static analysis tool indicates that null
pointer dereference may exist in pointer zone->per_cpu_pageset. It is
always safe to judge the null pointer before use.

Signed-off-by: Qiu-ji Chen <chenqiuji666@...il.com>
Cc: stable@...r.kernel.org
Fixes: 9420f89db2dd ("mm: move most of core MM initialization to mm/mm_init.c")
---
 mm/page_alloc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8afab64814dc..5deae1193dc3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5703,8 +5703,14 @@ void __meminit setup_zone_pageset(struct zone *zone)
 	/* Size may be 0 on !SMP && !NUMA */
 	if (sizeof(struct per_cpu_zonestat) > 0)
 		zone->per_cpu_zonestats = alloc_percpu(struct per_cpu_zonestat);
+	if (!zone->per_cpu_pageset)
+		return;
 
 	zone->per_cpu_pageset = alloc_percpu(struct per_cpu_pages);
+	if (!zone->per_cpu_pageset) {
+		free_percpu(zone->per_cpu_pageset);
+		return;
+	}
 	for_each_possible_cpu(cpu) {
 		struct per_cpu_pages *pcp;
 		struct per_cpu_zonestat *pzstats;
-- 
2.34.1