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SubjectRe: [PATCH] drivers/net/wimax/i2400m/fw.c fix possible double free
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On Wed, 2010-03-17 at 05:40 -0700, Darren Jenkins wrote: 
> On Wed, Mar 17, 2010 at 8:14 AM, David Miller <davem@davemloft.net>
> wrote:
>
> > Therefore the krealloc() failure handling in this driver should NULL
> > out i2400m->fw_hdrs and that will fix the double kfree problem as well
> > as trap any stray references.
>
> Yes that is a much better Idea. Thanks for the advice.
> It also fixes the i2400m_barker_db problem that I didn't notice before.
>
>
> Fix double free on krealloc() failure by zeroing pointer

If krealloc() fails to aallocate a new pointer, the old block is
unmodified, so by doing this you are leaking a buffer allocation.

I think this should be solved at the site where i2400m_zrealloc_2x() is
called, with a

if (result < 0) {
kfree(i2400m->fw_hdrs);
i2400m->fw_hdrs = NULL;
goto error_zrealloc;
}
or any other better fix. I am hesitant of having zrealloc_2x free the
original pointer because it breaks the traditional semantics that come
along being called 'realloc' (realloc if successful, keep the original
if not).

Am I missing anything?


> coverity CID: 13455
>
> Signed-off-by: Darren Jenkins <darrenrjenkins@gmail.com>
> ---
> drivers/net/wimax/i2400m/fw.c | 5 +++--
> 1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wimax/i2400m/fw.c b/drivers/net/wimax/i2400m/fw.c
> index 25c24f0..9f3b594 100644
> --- a/drivers/net/wimax/i2400m/fw.c
> +++ b/drivers/net/wimax/i2400m/fw.c
> @@ -232,8 +232,9 @@ int i2400m_zrealloc_2x(void **ptr, size_t *_count, size_t el_size,
> *_count = new_count;
> *ptr = nptr;
> return 0;
> - } else
> - return -ENOMEM;
> + }
> + *ptr = NULL;
> + return -ENOMEM;
> }
>
>





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