[PATCH] block: bio: use struct_size() in kmalloc()

[PATCH] block: bio: use struct_size() in kmalloc()

[xiaolinkui]

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>
---
 block/bio.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 683cbb4..847ac60 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -436,9 +436,7 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, unsigned int nr_iovecs,
 		if (nr_iovecs > UIO_MAXIOV)
 			return NULL;
 
-		p = kmalloc(sizeof(struct bio) +
-			    nr_iovecs * sizeof(struct bio_vec),
-			    gfp_mask);
+		p = kmalloc(struct_size(bio, bi_io_vec, nr_iovecs), gfp_mask);
 		front_pad = 0;
 		inline_vecs = nr_iovecs;
 	} else {
@@ -1120,8 +1118,7 @@ static struct bio_map_data *bio_alloc_map_data(struct iov_iter *data,
 	if (data->nr_segs > UIO_MAXIOV)
 		return NULL;
 
-	bmd = kmalloc(sizeof(struct bio_map_data) +
-		       sizeof(struct iovec) * data->nr_segs, gfp_mask);
+	bmd = kmalloc(struct_size(bmd, iov, data->nr_segs), gfp_mask);
 	if (!bmd)
 		return NULL;
 	memcpy(bmd->iov, data->iov, sizeof(struct iovec) * data->nr_segs);
-- 
2.7.4

Re: [PATCH] block: bio: use struct_size() in kmalloc()

[Chaitanya Kulkarni]

Looks good.

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

On 5/17/19 2:17 AM, xiaolinkui wrote:
> 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>
> ---
>  block/bio.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 683cbb4..847ac60 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -436,9 +436,7 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, unsigned int nr_iovecs,
>  		if (nr_iovecs > UIO_MAXIOV)
>  			return NULL;
>  
> -		p = kmalloc(sizeof(struct bio) +
> -			    nr_iovecs * sizeof(struct bio_vec),
> -			    gfp_mask);
> +		p = kmalloc(struct_size(bio, bi_io_vec, nr_iovecs), gfp_mask);
>  		front_pad = 0;
>  		inline_vecs = nr_iovecs;
>  	} else {
> @@ -1120,8 +1118,7 @@ static struct bio_map_data *bio_alloc_map_data(struct iov_iter *data,
>  	if (data->nr_segs > UIO_MAXIOV)
>  		return NULL;
>  
> -	bmd = kmalloc(sizeof(struct bio_map_data) +
> -		       sizeof(struct iovec) * data->nr_segs, gfp_mask);
> +	bmd = kmalloc(struct_size(bmd, iov, data->nr_segs), gfp_mask);
>  	if (!bmd)
>  		return NULL;
>  	memcpy(bmd->iov, data->iov, sizeof(struct iovec) * data->nr_segs);

Re: [PATCH] block: bio: use struct_size() in kmalloc()

[Jens Axboe]

On 5/17/19 3:12 AM, xiaolinkui wrote:
> 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);

Applied, thanks.

-- 
Jens Axboe

Re: [PATCH] block: bio: use struct_size() in kmalloc()

[Jens Axboe]

On 5/17/19 3:17 PM, Jens Axboe wrote:
> On 5/17/19 3:12 AM, xiaolinkui wrote:
>> 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);
> 
> Applied, thanks.

I take that back, you obviously didn't even compile this patch. Never
send untested crap, without explicitly saying so.

-- 
Jens Axboe

[PATCH] block: bio: Use struct_size() in kmalloc()

[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 bio_map_data {
	...
        struct iovec iov[];
};

instance = kmalloc(sizeof(sizeof(struct bio_map_data) + sizeof(struct iovec) *
                          count, 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, iov, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 block/bio.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 683cbb40f051..4bcdcd3f63f4 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1120,8 +1120,7 @@ static struct bio_map_data *bio_alloc_map_data(struct iov_iter *data,
 	if (data->nr_segs > UIO_MAXIOV)
 		return NULL;
 
-	bmd = kmalloc(sizeof(struct bio_map_data) +
-		       sizeof(struct iovec) * data->nr_segs, gfp_mask);
+	bmd = kmalloc(struct_size(bmd, iov, data->nr_segs), gfp_mask);
 	if (!bmd)
 		return NULL;
 	memcpy(bmd->iov, data->iov, sizeof(struct iovec) * data->nr_segs);
-- 
2.21.0

Re: [PATCH] block: bio: Use struct_size() in kmalloc()

[Kees Cook]

On Mon, Jun 10, 2019 at 10:04:12AM -0500, Gustavo A. R. Silva wrote:
> 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 bio_map_data {
> 	...
>         struct iovec iov[];
> };
> 
> instance = kmalloc(sizeof(sizeof(struct bio_map_data) + sizeof(struct iovec) *
>                           count, 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, iov, count), GFP_KERNEL);
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
>  block/bio.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 683cbb40f051..4bcdcd3f63f4 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1120,8 +1120,7 @@ static struct bio_map_data *bio_alloc_map_data(struct iov_iter *data,
>  	if (data->nr_segs > UIO_MAXIOV)
>  		return NULL;
>  
> -	bmd = kmalloc(sizeof(struct bio_map_data) +
> -		       sizeof(struct iovec) * data->nr_segs, gfp_mask);
> +	bmd = kmalloc(struct_size(bmd, iov, data->nr_segs), gfp_mask);
>  	if (!bmd)
>  		return NULL;
>  	memcpy(bmd->iov, data->iov, sizeof(struct iovec) * data->nr_segs);
> -- 
> 2.21.0
> 

-- 
Kees Cook

Re: [PATCH] block: bio: Use struct_size() in kmalloc()

[Jens Axboe]

On 6/10/19 9:04 AM, Gustavo A. R. Silva wrote:
> 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 bio_map_data {
> 	...
>          struct iovec iov[];
> };
> 
> instance = kmalloc(sizeof(sizeof(struct bio_map_data) + sizeof(struct iovec) *
>                            count, 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, iov, count), GFP_KERNEL);
> 
> This code was detected with the help of Coccinelle.

Applied, thanks.

-- 
Jens Axboe