[PATCH net-next] libceph, ceph: use struct_size() in kmalloc()

[PATCH net-next] libceph, ceph: 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 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);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 net/ceph/osdmap.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
index 98c0ff3d6441..48a31dc9161c 100644
--- a/net/ceph/osdmap.c
+++ b/net/ceph/osdmap.c
@@ -495,9 +495,8 @@ static struct crush_map *crush_decode(void *pbyval, void *end)
 			  / sizeof(struct crush_rule_step))
 			goto bad;
 #endif
-		r = c->rules[i] = kmalloc(sizeof(*r) +
-					  yes*sizeof(struct crush_rule_step),
-					  GFP_NOFS);
+		r = kmalloc(struct_size(r, steps, yes), GFP_NOFS);
+		c->rules[i] = r;
 		if (r == NULL)
 			goto badmem;
 		dout(" rule %d is at %p\n", i, r);
-- 
2.20.1

Re: [PATCH net-next] libceph, ceph: use struct_size() in kmalloc()

[Ilya Dryomov]

On Tue, Jan 15, 2019 at 8:41 PM Gustavo A. R. Silva
<gustavo@embeddedor.com> 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);
>
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  net/ceph/osdmap.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
> index 98c0ff3d6441..48a31dc9161c 100644
> --- a/net/ceph/osdmap.c
> +++ b/net/ceph/osdmap.c
> @@ -495,9 +495,8 @@ static struct crush_map *crush_decode(void *pbyval, void *end)
>                           / sizeof(struct crush_rule_step))
>                         goto bad;
>  #endif
> -               r = c->rules[i] = kmalloc(sizeof(*r) +
> -                                         yes*sizeof(struct crush_rule_step),
> -                                         GFP_NOFS);
> +               r = kmalloc(struct_size(r, steps, yes), GFP_NOFS);
> +               c->rules[i] = r;
>                 if (r == NULL)
>                         goto badmem;
>                 dout(" rule %d is at %p\n", i, r);

Applied.

Thanks,

                Ilya

Re: [PATCH net-next] libceph, ceph: use struct_size() in kmalloc()

[Gustavo A. R. Silva]

On 1/17/19 8:17 AM, Ilya Dryomov wrote:
> On Tue, Jan 15, 2019 at 8:41 PM Gustavo A. R. Silva
> <gustavo@embeddedor.com> 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);
>>
>> This code was detected with the help of Coccinelle.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>> ---
>>  net/ceph/osdmap.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
>> index 98c0ff3d6441..48a31dc9161c 100644
>> --- a/net/ceph/osdmap.c
>> +++ b/net/ceph/osdmap.c
>> @@ -495,9 +495,8 @@ static struct crush_map *crush_decode(void *pbyval, void *end)
>>                           / sizeof(struct crush_rule_step))
>>                         goto bad;
>>  #endif
>> -               r = c->rules[i] = kmalloc(sizeof(*r) +
>> -                                         yes*sizeof(struct crush_rule_step),
>> -                                         GFP_NOFS);
>> +               r = kmalloc(struct_size(r, steps, yes), GFP_NOFS);
>> +               c->rules[i] = r;
>>                 if (r == NULL)
>>                         goto badmem;
>>                 dout(" rule %d is at %p\n", i, r);
> 
> Applied.
> 

Thanks, Ilya.

--
Gustavo