Re: PATCH: Fix poor pointer math in devinet_sysctl_register

From: Mikael Pettersson
Date: Thu Nov 17 2005 - 05:57:56 EST


Jordan Crouse writes:
> This patch fixes pointer math that under certain circumstances, results
> in really bad pointers. This was encountered on a system compiled for i486, so
> other compilers may differ, but I don't think it hurts anyone.
>
> Signed-off-by: Jordan Crouse <jordan.crouse@xxxxxxx>
> ---
>
> net/ipv4/devinet.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index 4ec4b2c..7585fce 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -1454,7 +1454,7 @@ static void devinet_sysctl_register(stru
> return;
> memcpy(t, &devinet_sysctl, sizeof(*t));
> for (i = 0; i < ARRAY_SIZE(t->devinet_vars) - 1; i++) {
> - t->devinet_vars[i].data += (char *)p - (char *)&ipv4_devconf;
> + t->devinet_vars[i].data += (int)((char *)p - (char *)&ipv4_devconf);
> t->devinet_vars[i].de = NULL;
> }

This is the same code which broke due to a known gcc-4.0.0 bug:
<http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21173>. If you're
indeed using gcc-4.0.0, then it's time to upgrade.

/Mikael
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