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qxl: Use struct_size() in kzalloc()

PATCH In review Gustavo A. R. Silva 2 participants 3 messages Jan 8, 2019 – Jan 9, 2019

Subsystems (4)
DRM drivers DRM misc virtio core DRM driver for QXL virtual GPU
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Gustavo A. R. Silva

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#0 lore raw

PATCH 1/1 qxl: Use struct_size() in kzalloc()

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) + sizeof(void *) * count, 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 <[email protected]>
---
 drivers/gpu/drm/qxl/qxl_display.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
drivers/gpu/drm/qxl/qxl_display.c +2 -2
index ce0b9c40fc21..c8642712412e 100644
@@ -48,8 +48,8 @@ static int qxl_alloc_client_monitors_config(struct qxl_device *qdev,
 	}
 	if (!qdev->client_monitors_config) {
 		qdev->client_monitors_config = kzalloc(
-				sizeof(struct qxl_monitors_config) +
-				sizeof(struct qxl_head) * count, GFP_KERNEL);
+				struct_size(qdev->client_monitors_config,
+				heads, count), GFP_KERNEL);
 		if (!qdev->client_monitors_config)
 			return -ENOMEM;
 	}
Signature · 1 line
2.20.1
maintainer
#1 lore raw
Quoted 9 lines · Gustavo A. R. Silva

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[];
};
Quoted 8 lines

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, 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.

Patch queued up.

thanks,
Gerd

maintainer
#2 lore raw
In reply to Gustavo A. R. Silva
Quoted 9 lines · Gustavo A. R. Silva

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[];
};
Quoted 8 lines

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, 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.

Patch queued up.

thanks,
Gerd