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Subject[patch 1/4 -mm] flex_array: convert element_nr formals to unsigned
It's problematic to allow signed element_nr's or total's to be passed as
part of the flex array API.

flex_array_alloc() allows total_nr_elements to be set to a negative
quantity, which is obviously erroneous.

flex_array_get() and flex_array_put() allows negative array indices in
dereferencing an array part, which could address memory mapped before
struct flex_array.

The fix is to convert all existing element_nr formals to be qualified as
unsigned. Existing checks to compare it to total_nr_elements or the max
array size based on element_size need not be changed.

Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
include/linux/flex_array.h | 10 ++++++----
lib/flex_array.c | 24 +++++++++++++-----------
2 files changed, 19 insertions(+), 15 deletions(-)
diff --git a/include/linux/flex_array.h b/include/linux/flex_array.h
--- a/include/linux/flex_array.h
+++ b/include/linux/flex_array.h
@@ -36,12 +36,14 @@ struct flex_array {
.total_nr_elements = (total), \
} } }

-struct flex_array *flex_array_alloc(int element_size, int total, gfp_t flags);
-int flex_array_prealloc(struct flex_array *fa, int start, int end, gfp_t flags);
+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);
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, int element_nr, void *src,
+int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
gfp_t flags);
-void *flex_array_get(struct flex_array *fa, int element_nr);
+void *flex_array_get(struct flex_array *fa, unsigned int element_nr);

#endif /* _FLEX_ARRAY_H */
diff --git a/lib/flex_array.c b/lib/flex_array.c
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -99,7 +99,8 @@ static inline int elements_fit_in_base(struct flex_array *fa)
* capacity in the base structure. Also note that no effort is made
* to efficiently pack objects across page boundaries.
*/
-struct flex_array *flex_array_alloc(int element_size, int total, gfp_t flags)
+struct flex_array *flex_array_alloc(int element_size, unsigned int total,
+ gfp_t flags)
{
struct flex_array *ret;
int max_size = nr_base_part_ptrs() * __elements_per_part(element_size);
@@ -115,7 +116,8 @@ struct flex_array *flex_array_alloc(int element_size, int total, gfp_t flags)
return ret;
}

-static int fa_element_to_part_nr(struct flex_array *fa, int element_nr)
+static int fa_element_to_part_nr(struct flex_array *fa,
+ unsigned int element_nr)
{
return element_nr / __elements_per_part(fa->element_size);
}
@@ -143,14 +145,12 @@ void flex_array_free(struct flex_array *fa)
kfree(fa);
}

-static int fa_index_inside_part(struct flex_array *fa, int element_nr)
+static unsigned int index_inside_part(struct flex_array *fa,
+ unsigned int element_nr)
{
- return element_nr % __elements_per_part(fa->element_size);
-}
+ unsigned int part_offset;

-static int index_inside_part(struct flex_array *fa, int element_nr)
-{
- int part_offset = fa_index_inside_part(fa, element_nr);
+ part_offset = element_nr % __elements_per_part(fa->element_size);
return part_offset * fa->element_size;
}

@@ -185,7 +185,8 @@ __fa_get_part(struct flex_array *fa, int part_nr, gfp_t flags)
*
* Locking must be provided by the caller.
*/
-int flex_array_put(struct flex_array *fa, int element_nr, void *src, 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);
struct flex_array_part *part;
@@ -217,7 +218,8 @@ int flex_array_put(struct flex_array *fa, int element_nr, void *src, gfp_t flags
*
* Locking must be provided by the caller.
*/
-int flex_array_prealloc(struct flex_array *fa, int start, int end, gfp_t flags)
+int flex_array_prealloc(struct flex_array *fa, unsigned int start,
+ unsigned int end, gfp_t flags)
{
int start_part;
int end_part;
@@ -248,7 +250,7 @@ int flex_array_prealloc(struct flex_array *fa, int start, int end, gfp_t flags)
*
* Locking must be provided by the caller.
*/
-void *flex_array_get(struct flex_array *fa, int element_nr)
+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;

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