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net: dsa: use struct_size() in devm_kzalloc()

PATCH Applied Gustavo A. R. Silva 3 participants 3 messages Feb 8, 2019 – Feb 9, 2019

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Gustavo A. R. Silva

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#0 lore raw

PATCH 1/1 net: dsa: use struct_size() in devm_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;
    struct boo entry[];
};

size = sizeof(struct foo) + count * sizeof(struct boo); instance = alloc(size, GFP_KERNEL)

Instead of leaving these open-coded and prone to type mistakes, we can now use the new struct_size() helper:

instance = alloc(struct_size(instance, entry, count), GFP_KERNEL)

Notice that, in this case, variable size is not necessary, hence it is removed.

This code was detected with the help of Coccinelle.

Signed-off-by Gustavo A. R. Silva <[email protected]>
---
 net/dsa/dsa2.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
net/dsa/dsa2.c +1 -2
index a1917025e155..8c431e0f3627 100644
@@ -767,11 +767,10 @@ static int dsa_switch_probe(struct dsa_switch *ds)
 
 struct dsa_switch *dsa_switch_alloc(struct device *dev, size_t n)
 {
-	size_t size = sizeof(struct dsa_switch) + n * sizeof(struct dsa_port);
 	struct dsa_switch *ds;
 	int i;
 
-	ds = devm_kzalloc(dev, size, GFP_KERNEL);
+	ds = devm_kzalloc(dev, struct_size(ds, ports, n), GFP_KERNEL);
 	if (!ds)
 		return NULL;
Signature · 1 line
2.20.1
Reviewed-by on v1 1/1
#1 lore raw
Quoted 15 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;
    struct boo entry[];
};

size = sizeof(struct foo) + count * sizeof(struct boo); instance = alloc(size, GFP_KERNEL)

Instead of leaving these open-coded and prone to type mistakes, we can now use the new struct_size() helper:

Quoted 8 lines

instance = alloc(struct_size(instance, entry, count), GFP_KERNEL)

Notice that, in this case, variable size is not necessary, hence it is removed.

This code was detected with the help of Coccinelle.

Signed-off-by Gustavo A. R. Silva <[email protected]>
Reviewed-by Vivien Didelot <[email protected]>
maintainer Applied
#2 lore raw
In reply to Gustavo A. R. Silva

From: "Gustavo A. R. Silva" <[email protected]>
Date: Thu, 7 Feb 2019 19:16:03 -0600

Quoted 15 lines

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;
    struct boo entry[];
};

size = sizeof(struct foo) + count * sizeof(struct boo); instance = alloc(size, GFP_KERNEL)

Instead of leaving these open-coded and prone to type mistakes, we can now use the new struct_size() helper:

Quoted 8 lines

instance = alloc(struct_size(instance, entry, count), GFP_KERNEL)

Notice that, in this case, variable size is not necessary, hence it is removed.

This code was detected with the help of Coccinelle.

Signed-off-by Gustavo A. R. Silva <[email protected]>

Applied.