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From: "Gustavo A. R. Silva" <gustavoars@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	cgroups@vger.kernel.org, linux-mm@kvack.org,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>
Subject: [PATCH 1/2][next] mm: memcontrol: Use flex_array_size() helper in memcpy()
Date: Fri, 31 Jul 2020 12:12:53 -0500	[thread overview]
Message-ID: <ddd60dae2d9aea1ccdd2be66634815c93696125e.1596214831.git.gustavoars@kernel.org> (raw)
In-Reply-To: <cover.1596214831.git.gustavoars@kernel.org>

Make use of the flex_array_size() helper to calculate the size of a
flexible array member within an enclosing structure.

This helper offers defense-in-depth against potential integer
overflows, while at the same time makes it explicitly clear that
we are dealing with a flexible array member.

Also, remove unnecessary braces.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 mm/memcontrol.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e84c2b5596f2..bd7f972ceea4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4246,10 +4246,9 @@ static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
 	new->size = size;
 
 	/* Copy thresholds (if any) to new array */
-	if (thresholds->primary) {
-		memcpy(new->entries, thresholds->primary->entries, (size - 1) *
-				sizeof(struct mem_cgroup_threshold));
-	}
+	if (thresholds->primary)
+		memcpy(new->entries, thresholds->primary->entries,
+		       flex_array_size(new, entries, size - 1));
 
 	/* Add new threshold */
 	new->entries[size - 1].eventfd = eventfd;
-- 
2.27.0


WARNING: multiple messages have this Message-ID (diff)
From: "Gustavo A. R. Silva" <gustavoars-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
	Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Vladimir Davydov
	<vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	"Gustavo A. R. Silva"
	<gustavoars-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: [PATCH 1/2][next] mm: memcontrol: Use flex_array_size() helper in memcpy()
Date: Fri, 31 Jul 2020 12:12:53 -0500	[thread overview]
Message-ID: <ddd60dae2d9aea1ccdd2be66634815c93696125e.1596214831.git.gustavoars@kernel.org> (raw)
In-Reply-To: <cover.1596214831.git.gustavoars-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

Make use of the flex_array_size() helper to calculate the size of a
flexible array member within an enclosing structure.

This helper offers defense-in-depth against potential integer
overflows, while at the same time makes it explicitly clear that
we are dealing with a flexible array member.

Also, remove unnecessary braces.

Signed-off-by: Gustavo A. R. Silva <gustavoars-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 mm/memcontrol.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e84c2b5596f2..bd7f972ceea4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4246,10 +4246,9 @@ static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
 	new->size = size;
 
 	/* Copy thresholds (if any) to new array */
-	if (thresholds->primary) {
-		memcpy(new->entries, thresholds->primary->entries, (size - 1) *
-				sizeof(struct mem_cgroup_threshold));
-	}
+	if (thresholds->primary)
+		memcpy(new->entries, thresholds->primary->entries,
+		       flex_array_size(new, entries, size - 1));
 
 	/* Add new threshold */
 	new->entries[size - 1].eventfd = eventfd;
-- 
2.27.0


  reply	other threads:[~2020-07-31 17:06 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-31 17:12 [PATCH 0/2][next] Use flexible_array_size() helper in memcpy() Gustavo A. R. Silva
2020-07-31 17:12 ` Gustavo A. R. Silva
2020-07-31 17:12 ` Gustavo A. R. Silva [this message]
2020-07-31 17:12   ` [PATCH 1/2][next] mm: memcontrol: Use flex_array_size() " Gustavo A. R. Silva
2020-08-04 13:25   ` Michal Hocko
2020-07-31 17:13 ` [PATCH 2/2][next] mm: memcontrol: Use the preferred form for passing the size of a structure type Gustavo A. R. Silva
2020-07-31 17:13   ` Gustavo A. R. Silva
2020-08-04 13:25   ` Michal Hocko
2020-08-04 13:25     ` Michal Hocko

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