[rds-devel] [patch] RDS: fix an integer overflow check
Jeff Liu
jeff.liu at oracle.com
Sat Oct 13 06:25:40 PDT 2012
On 10/12/2012 03:31 PM, Dan Carpenter wrote:
> "len" is an int. We verified that len was postive already. Since
> PAGE_SIZE is specified as an unsigned long, the type it promoted to
> unsigned and the condition is never true.
>
> I'm not sure this check is actually needed. It might be that we could
> just remove it?
>
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
>
> diff --git a/net/rds/info.c b/net/rds/info.c
> index 9a6b4f6..4d62618 100644
> --- a/net/rds/info.c
> +++ b/net/rds/info.c
> @@ -176,7 +176,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
>
> /* check for all kinds of wrapping and the like */
> start = (unsigned long)optval;
> - if (len < 0 || len + PAGE_SIZE - 1 < len || start + len < start) {
Looks the original thought is to check up len + (PAGE_SIZE - 1) < len to
avoid integer overflow, but lack of a "()".
However, we only have one add operation in this function which were
shown as following:
nr_pages = (PAGE_ALIGN(start + len) - (start & PAGE_MASK))
>> PAGE_SHIFT;
I also gone through the call chains, there is no other (start + len)
operations for all transport, I think it's safe to remove this check up
if so.
Thanks,
-Jeff
> + if (len < 0 || len > INT_MAX - (PAGE_SIZE - 1) || start + len < start) {
> ret = -EINVAL;
> goto out;
> }
> --
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