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Subject[PATCH] flex_array: Change behaviour on zero size allocations
flex_array_alloc allocates the basic struct flex_array regardless whether
total_nr_elements or element_size is zero. Then flex_array_prealloc
fails with -ENOSPC if total_nr_elements is zero or it hits a division by
zero if element_size is zero.

This patch changes the behaviour on zero size allocations to the same
as kmalloc, so zero size allocations are leagal now. This fixes a
regression on selinux policy loading.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
---
lib/flex_array.c | 25 +++++++++++++++++++++----
1 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/lib/flex_array.c b/lib/flex_array.c
index c0ea40b..8eb437b 100644
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -88,8 +88,11 @@ struct flex_array *flex_array_alloc(int element_size, unsigned int total,
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 @@ __fa_get_part(struct flex_array *fa, int part_nr, gfp_t flags)
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 (!fa->element_size)
+ return 0;
if (element_nr >= fa->total_nr_elements)
return -ENOSPC;
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 @@ EXPORT_SYMBOL(flex_array_put);
*/
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 (!fa->element_size)
+ return 0;
if (element_nr >= fa->total_nr_elements)
return -ENOSPC;
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;
@@ -252,8 +261,12 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start,
int part_nr;
struct flex_array_part *part;

+ if (!fa->total_nr_elements)
+ return 0;
if (start >= fa->total_nr_elements || 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);
@@ -284,6 +297,8 @@ void *flex_array_get(struct flex_array *fa, unsigned int element_nr)
int part_nr = fa_element_to_part_nr(fa, element_nr);
struct flex_array_part *part;

+ if (!fa->total_nr_elements || !fa->element_size)
+ return NULL;
if (element_nr >= fa->total_nr_elements)
return NULL;
if (elements_fit_in_base(fa))
@@ -343,6 +358,8 @@ int flex_array_shrink(struct flex_array *fa)
int part_nr;
int ret = 0;

+ if (!fa->total_nr_elements || !fa->element_size)
+ return 0;
if (elements_fit_in_base(fa))
return ret;
for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++) {
--
1.7.0.4


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