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Message-ID: <20110207122903.GO3070@secunet.com>
Date: Mon, 7 Feb 2011 13:29:03 +0100
From: Steffen Klassert <steffen.klassert@...unet.com>
To: Dave Hansen <dave@...ux.vnet.ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Eric Paris <eparis@...hat.com>, linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org
Subject: [PATCH v2] 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. We also change
flex_array_prealloc to take the number of elements for which space
should be allocated instead of the last (inclusive) element. Users
and documentation are updated accordingly.
This fixes a regression on selinux policy loading.
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
---
Documentation/flexible-arrays.txt | 4 +-
include/linux/flex_array.h | 2 +-
lib/flex_array.c | 48 ++++++++++++++++++++++++++++--------
security/selinux/ss/policydb.c | 6 ++--
4 files changed, 43 insertions(+), 17 deletions(-)
diff --git a/Documentation/flexible-arrays.txt b/Documentation/flexible-arrays.txt
index cb8a3a0..df904ae 100644
--- a/Documentation/flexible-arrays.txt
+++ b/Documentation/flexible-arrays.txt
@@ -66,10 +66,10 @@ trick is to ensure that any needed memory allocations are done before
entering atomic context, using:
int flex_array_prealloc(struct flex_array *array, unsigned int start,
- unsigned int end, gfp_t flags);
+ unsigned int nr_elements, gfp_t flags);
This function will ensure that memory for the elements indexed in the range
-defined by start and end has been allocated. Thereafter, a
+defined by start and nr_elements has been allocated. Thereafter, a
flex_array_put() call on an element in that range is guaranteed not to
block.
diff --git a/include/linux/flex_array.h b/include/linux/flex_array.h
index 70e4efa..ebeb2f3 100644
--- a/include/linux/flex_array.h
+++ b/include/linux/flex_array.h
@@ -61,7 +61,7 @@ struct flex_array {
struct flex_array *flex_array_alloc(int element_size, unsigned int total,
gfp_t flags);
int flex_array_prealloc(struct flex_array *fa, unsigned int start,
- unsigned int end, gfp_t flags);
+ unsigned int nr_elements, gfp_t flags);
void flex_array_free(struct flex_array *fa);
void flex_array_free_parts(struct flex_array *fa);
int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
diff --git a/lib/flex_array.c b/lib/flex_array.c
index c0ea40b..dcd91d5 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 (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 @@ 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 (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;
@@ -232,10 +241,10 @@ EXPORT_SYMBOL(flex_array_clear);
/**
* flex_array_prealloc - guarantee that array space exists
- * @fa: the flex array for which to preallocate parts
- * @start: index of first array element for which space is allocated
- * @end: index of last (inclusive) element for which space is allocated
- * @flags: page allocation flags
+ * @fa: the flex array for which to preallocate parts
+ * @start: index of first array element for which space is allocated
+ * @nr_elements: number of elements for which space is allocated
+ * @flags: page allocation flags
*
* This will guarantee that no future calls to flex_array_put()
* will allocate memory. It can be used if you are expecting to
@@ -245,15 +254,27 @@ EXPORT_SYMBOL(flex_array_clear);
* Locking must be provided by the caller.
*/
int flex_array_prealloc(struct flex_array *fa, unsigned int start,
- unsigned int end, gfp_t flags)
+ unsigned int nr_elements, gfp_t flags)
{
int start_part;
int end_part;
int part_nr;
+ unsigned int end;
struct flex_array_part *part;
- if (start >= fa->total_nr_elements || end >= fa->total_nr_elements)
+ if (!fa->total_nr_elements && !start)
+ return 0;
+ if (start >= fa->total_nr_elements)
+ return -ENOSPC;
+ if (!nr_elements)
+ return 0;
+
+ end = start + nr_elements - 1;
+
+ 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);
@@ -281,14 +302,17 @@ EXPORT_SYMBOL(flex_array_prealloc);
*/
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;
@@ -343,6 +367,8 @@ 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++) {
diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 5736356..f96f09c 100644
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -497,7 +497,7 @@ static int policydb_index(struct policydb *p)
goto out;
rc = flex_array_prealloc(p->type_val_to_struct_array, 0,
- p->p_types.nprim - 1, GFP_KERNEL | __GFP_ZERO);
+ p->p_types.nprim, GFP_KERNEL | __GFP_ZERO);
if (rc)
goto out;
@@ -514,7 +514,7 @@ static int policydb_index(struct policydb *p)
goto out;
rc = flex_array_prealloc(p->sym_val_to_name[i],
- 0, p->symtab[i].nprim - 1,
+ 0, p->symtab[i].nprim,
GFP_KERNEL | __GFP_ZERO);
if (rc)
goto out;
@@ -2286,7 +2286,7 @@ int policydb_read(struct policydb *p, void *fp)
goto bad;
/* preallocate so we don't have to worry about the put ever failing */
- rc = flex_array_prealloc(p->type_attr_map_array, 0, p->p_types.nprim - 1,
+ rc = flex_array_prealloc(p->type_attr_map_array, 0, p->p_types.nprim,
GFP_KERNEL | __GFP_ZERO);
if (rc)
goto bad;
--
1.7.0.4
--
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