drm/vc4: Use struct_size() in kzalloc()

GustavoARSilva · anholt · commit 1eb6ea4a8202 · 2019-02-06T15:16:08.000-08:00
One of the more common cases of allocation size calculations is finding the size of a structure that has a zero-sized array at the end, along with memory for some number of elements for that array. For example: struct foo { int stuff; void *entry[]; }; instance = kzalloc(sizeof(struct foo) + count * sizeof(struct boo), GFP_KERNEL); Instead of leaving these open-coded and prone to type mistakes, we can now use the new struct_size() helper: instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL); This code was detected with the help of Coccinelle. Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> Signed-off-by: Eric Anholt <eric@anholt.net> Reviewed-by: Eric Anholt <eric@anholt.net> Link: https://patchwork.freedesktop.org/patch/msgid/20190131010015.GA32272@embeddedor
diff --git a/drivers/gpu/drm/vc4/vc4_perfmon.c b/drivers/gpu/drm/vc4/vc4_perfmon.c
@@ -117,7 +117,7 @@ int vc4_perfmon_create_ioctl(struct drm_device *dev, void *data,
 			return -EINVAL;
 	}
 
-	perfmon = kzalloc(sizeof(*perfmon) + (req->ncounters * sizeof(u64)),
+	perfmon = kzalloc(struct_size(perfmon, counters, req->ncounters),
 			  GFP_KERNEL);
 	if (!perfmon)
 		return -ENOMEM;

Original file line number	Diff line number	Diff line change
`@@ -117,7 +117,7 @@ int vc4_perfmon_create_ioctl(struct drm_device dev, void data,`
`117`	`117`	`return -EINVAL;`
`118`	`118`	`}`
`119`	`119`
`120`		`- perfmon = kzalloc(sizeof(perfmon) + (req->ncounters sizeof(u64)),`
	`120`	`+ perfmon = kzalloc(struct_size(perfmon, counters, req->ncounters),`
`121`	`121`	`GFP_KERNEL);`
`122`	`122`	`if (!perfmon)`
`123`	`123`	`return -ENOMEM;`