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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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