linux-kernel - [PATCH v2 1/2] mm: cma: fix the name of CMA areas

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Date:   Wed, 17 Jun 2020 10:31:30 +1200
From:   Barry Song <song.bao.hua@...ilicon.com>
To:     <akpm@...ux-foundation.org>, <mike.kravetz@...cle.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>, Barry Song <song.bao.hua@...ilicon.com>,
        "Roman Gushchin" <guro@...com>
Subject: [PATCH v2 1/2] mm: cma: fix the name of CMA areas

if users give a name saved in stack, the current code will generate magic
pointer.
if users don't give a name(NULL), kasprintf() will always return NULL as
we are at the early stage. that means cma_init_reserved_mem() will return
-ENOMEM if users set name parameter as NULL.

Acked-by: Roman Gushchin <guro@...com>
Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
Signed-off-by: Barry Song <song.bao.hua@...ilicon.com>
---
 -v2:
 rebase to 5.8-rc1
 add acked-by and reviewed-by

 mm/cma.c | 13 ++++++-------
 mm/cma.h |  4 +++-
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/mm/cma.c b/mm/cma.c
index 0463ad2ce06b..b24151fa2101 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -202,13 +202,12 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
 	 * subsystems (like slab allocator) are available.
 	 */
 	cma = &cma_areas[cma_area_count];
-	if (name) {
-		cma->name = name;
-	} else {
-		cma->name = kasprintf(GFP_KERNEL, "cma%d\n", cma_area_count);
-		if (!cma->name)
-			return -ENOMEM;
-	}
+
+	if (name)
+		snprintf(cma->name, CMA_MAX_NAME, name);
+	else
+		snprintf(cma->name, CMA_MAX_NAME,  "cma%d\n", cma_area_count);
+
 	cma->base_pfn = PFN_DOWN(base);
 	cma->count = size >> PAGE_SHIFT;
 	cma->order_per_bit = order_per_bit;
diff --git a/mm/cma.h b/mm/cma.h
index 33c0b517733c..27d3f0e9f68f 100644
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -2,6 +2,8 @@
 #ifndef __MM_CMA_H__
 #define __MM_CMA_H__
 
+#define CMA_MAX_NAME 64
+
 struct cma {
 	unsigned long   base_pfn;
 	unsigned long   count;
@@ -12,7 +14,7 @@ struct cma {
 	struct hlist_head mem_head;
 	spinlock_t mem_head_lock;
 #endif
-	const char *name;
+	char name[CMA_MAX_NAME];
 };
 
 extern struct cma cma_areas[MAX_CMA_AREAS];
-- 
2.23.0