Dan Carpenter wrote:
> On Fri, Aug 24, 2012 at 01:23:29PM +0200, Jim Meyering wrote:
>> In that case, what would you think of a patch to use strcpy instead?
>>
>> - strncpy(object->comm, current->comm, sizeof(object->comm));
>> + strcpy(object->comm, current->comm);
>
> Another option would be to use strlcpy(). It's slightly neater than
> the strncpy() followed by a NUL assignment.
>
>> Is there a preferred method of adding a static_assert-like statement?
>> I see compile_time_assert and a few similar macros, but I haven't
>> spotted anything that is used project-wide.
>
> BUILD_BUG_ON().
Hi Dan,
Thanks for the feedback and tip. How about this patch?
-- >8 --
Subject: [PATCH] kmemleak: remove unwarranted uses of strncpy
Use of strncpy was not justified -- was misleading, in fact, since
none of the three uses could trigger strncpy's truncation feature,
nor did they require the NUL-padding it can provide. Replace each
use with a BUG_ON_BUILD to ensure that the existing constraint
(source string is no larger than the size of the destination buffer)
and a use of strcpy. With the literals, it's easy to see that each
is shorter than TASK_COMM_LEN (aka, 16). In the third case, the
source and destination buffer have the same length, so there is no
possibility of truncation.
Signed-off-by: Jim Meyering <meyering@xxxxxxxxxx>
---
mm/kmemleak.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 45eb621..7359ffa 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -542,10 +542,12 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
/* task information */
if (in_irq()) {
object->pid = 0;
- strncpy(object->comm, "hardirq", sizeof(object->comm));
+ BUILD_BUG_ON(sizeof "hardirq" > sizeof(current->comm));
+ strcpy(object->comm, "hardirq");
} else if (in_softirq()) {
object->pid = 0;
- strncpy(object->comm, "softirq", sizeof(object->comm));
+ BUILD_BUG_ON(sizeof "softirq" > sizeof(current->comm));
+ strcpy(object->comm, "softirq");
} else {
object->pid = current->pid;
/*
@@ -554,7 +556,8 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
* dependency issues with current->alloc_lock. In the worst
* case, the command line is not correct.
*/
- strncpy(object->comm, current->comm, sizeof(object->comm));
+ BUILD_BUG_ON(sizeof (object->comm) > sizeof(current->comm));
+ strcpy(object->comm, current->comm);
}
/* kernel backtrace */
--
1.7.12.116.g31e0100
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