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 <[email protected]>
---
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
On Tue, Jan 15, 2019 at 8:41 PM Gustavo A. R. Silva
<[email protected]> 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 <[email protected]>
> ---
> 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
On 1/17/19 8:17 AM, Ilya Dryomov wrote:
> On Tue, Jan 15, 2019 at 8:41 PM Gustavo A. R. Silva
> <[email protected]> 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 <[email protected]>
>> ---
>> 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