[PATCH] nvme: target: use struct_size() in kmalloc()

[PATCH] nvme: target: use struct_size() in kmalloc()

[xiaolinkui]

Use struct_size() to keep code sample.
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[];
};

instance = kmalloc(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 = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);

Signed-off-by: xiaolinkui <xiaolinkui@kylinos.cn>
---
 drivers/nvme/target/admin-cmd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 9f72d51..6f9f830 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -248,8 +248,8 @@ static void nvmet_execute_get_log_page_ana(struct nvmet_req *req)
 	u16 status;
 
 	status = NVME_SC_INTERNAL;
-	desc = kmalloc(sizeof(struct nvme_ana_group_desc) +
-			NVMET_MAX_NAMESPACES * sizeof(__le32), GFP_KERNEL);
+	desc = kmalloc(struct_size(desc, nsids, NVMET_MAX_NAMESPACES),
+			GFP_KERNEL);
 	if (!desc)
 		goto out;
 
-- 
2.7.4

Re: [PATCH] nvme: target: use struct_size() in kmalloc()

[Chaitanya Kulkarni]

If maintainers are okay with this then,

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>

On 5/17/19 12:07 AM, xiaolinkui wrote:
> Use struct_size() to keep code sample.
> 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[];
> };
>
> instance = kmalloc(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 = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
>
> Signed-off-by: xiaolinkui <xiaolinkui@kylinos.cn>
> ---
>  drivers/nvme/target/admin-cmd.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
> index 9f72d51..6f9f830 100644
> --- a/drivers/nvme/target/admin-cmd.c
> +++ b/drivers/nvme/target/admin-cmd.c
> @@ -248,8 +248,8 @@ static void nvmet_execute_get_log_page_ana(struct nvmet_req *req)
>  	u16 status;
>  
>  	status = NVME_SC_INTERNAL;
> -	desc = kmalloc(sizeof(struct nvme_ana_group_desc) +
> -			NVMET_MAX_NAMESPACES * sizeof(__le32), GFP_KERNEL);
> +	desc = kmalloc(struct_size(desc, nsids, NVMET_MAX_NAMESPACES),
> +			GFP_KERNEL);
>  	if (!desc)
>  		goto out;
>  

Re: [PATCH] nvme: target: use struct_size() in kmalloc()

[Gustavo A. R. Silva]

On 5/17/19 2:03 AM, xiaolinkui wrote:
> Use struct_size() to keep code sample.

What do you mean by that?

> 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[];
> };
> 
> instance = kmalloc(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 = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
> 

How did you find this code?

If you used a tool like Coccinelle, mention it in the changelog text.

Did you compile it?

--
Gustavo

> Signed-off-by: xiaolinkui <xiaolinkui@kylinos.cn>
> ---
>  drivers/nvme/target/admin-cmd.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
> index 9f72d51..6f9f830 100644
> --- a/drivers/nvme/target/admin-cmd.c
> +++ b/drivers/nvme/target/admin-cmd.c
> @@ -248,8 +248,8 @@ static void nvmet_execute_get_log_page_ana(struct nvmet_req *req)
>  	u16 status;
>  
>  	status = NVME_SC_INTERNAL;
> -	desc = kmalloc(sizeof(struct nvme_ana_group_desc) +
> -			NVMET_MAX_NAMESPACES * sizeof(__le32), GFP_KERNEL);
> +	desc = kmalloc(struct_size(desc, nsids, NVMET_MAX_NAMESPACES),
> +			GFP_KERNEL);
>  	if (!desc)
>  		goto out;
>  
> 

Re: [PATCH] nvme: target: use struct_size() in kmalloc()

[Christoph Hellwig]

Looks ok to me, although for a fixed size argument the whole overflow
detection thing in struct_size() is rather pointless..