flex_array: allow 0 length elements
flex_arrays are supposed to be a replacement for:
kmalloc(num_elements * sizeof(element))
If kmalloc is given 0 num_elements or a 0 size element it will happily return
ZERO_SIZE_PTR. Which looks like a valid allocation, but which will explode if
something actually try to use it. The current flex_array code will return an
equivalent result if num_elements is 0, but will fail to work if
sizeof(element) is 0. This patch allows allocation to work even for 0 size
elements. It will cause flex_arrays to explode though if they are used.
Imitating the kmalloc behavior.
Based-on-patch-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Dave Hansen <dave@linux.vnet.ibm.com>
diff --git a/lib/flex_array.c b/lib/flex_array.c
index 854b57b..cab7621 100644
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -88,8 +88,11 @@
gfp_t flags)
{
struct flex_array *ret;
- int max_size = FLEX_ARRAY_NR_BASE_PTRS *
- FLEX_ARRAY_ELEMENTS_PER_PART(element_size);
+ int max_size = 0;
+
+ if (element_size)
+ max_size = FLEX_ARRAY_NR_BASE_PTRS *
+ FLEX_ARRAY_ELEMENTS_PER_PART(element_size);
/* max_size will end up 0 if element_size > PAGE_SIZE */
if (total > max_size)
@@ -183,15 +186,18 @@
int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
gfp_t flags)
{
- int part_nr = fa_element_to_part_nr(fa, element_nr);
+ int part_nr;
struct flex_array_part *part;
void *dst;
if (element_nr >= fa->total_nr_elements)
return -ENOSPC;
+ if (!fa->element_size)
+ return 0;
if (elements_fit_in_base(fa))
part = (struct flex_array_part *)&fa->parts[0];
else {
+ part_nr = fa_element_to_part_nr(fa, element_nr);
part = __fa_get_part(fa, part_nr, flags);
if (!part)
return -ENOMEM;
@@ -211,15 +217,18 @@
*/
int flex_array_clear(struct flex_array *fa, unsigned int element_nr)
{
- int part_nr = fa_element_to_part_nr(fa, element_nr);
+ int part_nr;
struct flex_array_part *part;
void *dst;
if (element_nr >= fa->total_nr_elements)
return -ENOSPC;
+ if (!fa->element_size)
+ return 0;
if (elements_fit_in_base(fa))
part = (struct flex_array_part *)&fa->parts[0];
else {
+ part_nr = fa_element_to_part_nr(fa, element_nr);
part = fa->parts[part_nr];
if (!part)
return -EINVAL;
@@ -264,6 +273,8 @@
if (end >= fa->total_nr_elements)
return -ENOSPC;
+ if (!fa->element_size)
+ return 0;
if (elements_fit_in_base(fa))
return 0;
start_part = fa_element_to_part_nr(fa, start);
@@ -291,14 +302,17 @@
*/
void *flex_array_get(struct flex_array *fa, unsigned int element_nr)
{
- int part_nr = fa_element_to_part_nr(fa, element_nr);
+ int part_nr;
struct flex_array_part *part;
+ if (!fa->element_size)
+ return NULL;
if (element_nr >= fa->total_nr_elements)
return NULL;
if (elements_fit_in_base(fa))
part = (struct flex_array_part *)&fa->parts[0];
else {
+ part_nr = fa_element_to_part_nr(fa, element_nr);
part = fa->parts[part_nr];
if (!part)
return NULL;
@@ -353,7 +367,7 @@
int part_nr;
int ret = 0;
- if (!fa->total_nr_elements)
+ if (!fa->total_nr_elements || !fa->element_size)
return 0;
if (elements_fit_in_base(fa))
return ret;