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SubjectRe: [patch 1/3] flex_array: fix get function for elements in base starting at non-zero
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On Mon, 2009-08-17 at 16:46 -0700, David Rientjes wrote:
> If all array elements fit into the base structure and data is copied
> using flex_array_put() starting at a non-zero index, flex_array_get()
> will fail to return the data.
>
> This fixes the bug by only checking for NULL parts when all elements do
> not fit in the base structure when flex_array_get() is used. Otherwise,
> fa_element_to_part_nr() will always be 0 since there are no parts
> structures needed and such element may never have been put. Thus, it
> will remain NULL due to the kzalloc() of the base.
>
> Additionally, flex_array_put() now only checks for a NULL part when all
> elements do not fit in the base structure. This is otherwise unnecessary
> since the base structure is guaranteed to exist (or we would have already
> hit a NULL pointer).
>
> Cc: Dave Hansen <dave@linux.vnet.ibm.com>
> Signed-off-by: David Rientjes <rientjes@google.com>
> ---
> lib/flex_array.c | 14 ++++++++------
> 1 files changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/lib/flex_array.c b/lib/flex_array.c
> --- a/lib/flex_array.c
> +++ b/lib/flex_array.c
> @@ -198,10 +198,11 @@ int flex_array_put(struct flex_array *fa, int element_nr, void *src, gfp_t flags
> return -ENOSPC;
> if (elements_fit_in_base(fa))
> part = (struct flex_array_part *)&fa->parts[0];
> - else
> + else {
> part = __fa_get_part(fa, part_nr, flags);
> - if (!part)
> - return -ENOMEM;
> + if (!part)
> + return -ENOMEM;
> + }
> dst = &part->elements[index_inside_part(fa, element_nr)];
> memcpy(dst, src, fa->element_size);
> return 0;
> @@ -257,11 +258,12 @@ void *flex_array_get(struct flex_array *fa, int element_nr)
>
> if (element_nr >= fa->total_nr_elements)
> return NULL;
> - if (!fa->parts[part_nr])
> - return NULL;
> if (elements_fit_in_base(fa))
> part = (struct flex_array_part *)&fa->parts[0];
> - else
> + else {
> part = fa->parts[part_nr];
> + if (!part)
> + return NULL;
> + }
> return &part->elements[index_inside_part(fa, element_nr)];
> }

This is fine with me, and fixes the bug you describe.

--

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>

-- Dave



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