Other mm routines such as kfree() and kzfree() silently do the right
thing if passed a NULL pointer, so ksize() should do the same.
Signed-off-by: William Kucharski <[email protected]>
---
mm/slab_common.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 9e72ba224175..2bff01ad94d8 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1660,10 +1660,9 @@ static __always_inline void *__do_krealloc(const void *p, size_t new_size,
gfp_t flags)
{
void *ret;
- size_t ks = 0;
+ size_t ks;
- if (p)
- ks = ksize(p);
+ ks = ksize(p);
if (ks >= new_size) {
p = kasan_krealloc((void *)p, new_size, flags);
@@ -1723,10 +1722,9 @@ void kzfree(const void *p)
size_t ks;
void *mem = (void *)p;
- if (unlikely(ZERO_OR_NULL_PTR(mem)))
- return;
ks = ksize(mem);
- memset(mem, 0, ks);
+ if (ks)
+ memset(mem, 0, ks);
kfree(mem);
}
EXPORT_SYMBOL(kzfree);
@@ -1749,8 +1747,6 @@ size_t ksize(const void *objp)
{
size_t size;
- if (WARN_ON_ONCE(!objp))
- return 0;
/*
* We need to check that the pointed to object is valid, and only then
* unpoison the shadow memory below. We use __kasan_check_read(), to
@@ -1764,7 +1760,7 @@ size_t ksize(const void *objp)
* We want to perform the check before __ksize(), to avoid potentially
* crashing in __ksize() due to accessing invalid metadata.
*/
- if (unlikely(objp == ZERO_SIZE_PTR) || !__kasan_check_read(objp, 1))
+ if (unlikely(ZERO_OR_NULL_PTR(objp)) || !__kasan_check_read(objp, 1))
return 0;
size = __ksize(objp);
--
2.26.2
On Tue, Jun 16, 2020 at 04:54:09PM -0600, William Kucharski wrote:
> Other mm routines such as kfree() and kzfree() silently do the right
> thing if passed a NULL pointer, so ksize() should do the same.
>
> Signed-off-by: William Kucharski <[email protected]>
Nice simplification.
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
On 17.06.20 00:54, William Kucharski wrote:
> Other mm routines such as kfree() and kzfree() silently do the right
> thing if passed a NULL pointer, so ksize() should do the same.
>
> Signed-off-by: William Kucharski <[email protected]>
> ---
> mm/slab_common.c | 14 +++++---------
> 1 file changed, 5 insertions(+), 9 deletions(-)
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 9e72ba224175..2bff01ad94d8 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1660,10 +1660,9 @@ static __always_inline void *__do_krealloc(const void *p, size_t new_size,
> gfp_t flags)
> {
> void *ret;
> - size_t ks = 0;
> + size_t ks;
>
> - if (p)
> - ks = ksize(p);
> + ks = ksize(p);
>
> if (ks >= new_size) {
> p = kasan_krealloc((void *)p, new_size, flags);
> @@ -1723,10 +1722,9 @@ void kzfree(const void *p)
> size_t ks;
> void *mem = (void *)p;
>
> - if (unlikely(ZERO_OR_NULL_PTR(mem)))
> - return;
> ks = ksize(mem);
> - memset(mem, 0, ks);
> + if (ks)
> + memset(mem, 0, ks);
> kfree(mem);
> }
> EXPORT_SYMBOL(kzfree);
> @@ -1749,8 +1747,6 @@ size_t ksize(const void *objp)
> {
> size_t size;
>
> - if (WARN_ON_ONCE(!objp))
> - return 0;
> /*
> * We need to check that the pointed to object is valid, and only then
> * unpoison the shadow memory below. We use __kasan_check_read(), to
> @@ -1764,7 +1760,7 @@ size_t ksize(const void *objp)
> * We want to perform the check before __ksize(), to avoid potentially
> * crashing in __ksize() due to accessing invalid metadata.
> */
> - if (unlikely(objp == ZERO_SIZE_PTR) || !__kasan_check_read(objp, 1))
> + if (unlikely(ZERO_OR_NULL_PTR(objp)) || !__kasan_check_read(objp, 1))
> return 0;
>
> size = __ksize(objp);
>
Reviewed-by: David Hildenbrand <[email protected]>
--
Thanks,
David / dhildenb
On Tue, 16 Jun 2020, William Kucharski wrote:
> Other mm routines such as kfree() and kzfree() silently do the right
> thing if passed a NULL pointer, so ksize() should do the same.
Ok so the size of an no object pointer is zero? Ignoring the freeing
of a nonexisting object makes sense. But determining it size?
On Wed, Jun 17, 2020 at 04:23:04PM +0000, Christopher Lameter wrote:
> On Tue, 16 Jun 2020, William Kucharski wrote:
>
> > Other mm routines such as kfree() and kzfree() silently do the right
> > thing if passed a NULL pointer, so ksize() should do the same.
>
> Ok so the size of an no object pointer is zero? Ignoring the freeing
> of a nonexisting object makes sense. But determining it size?
ksize() is misnamed. It's not the size of the object, it's the number
of bytes allocated for that object.
A NULL pointer represents a freed object, or one that was never
allocated in the first place. Clearly that's 0 bytes. What other
answer would make sense?