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Date: Sat, 13 Oct 2012 21:25:40 +0800
From: Jeff Liu <jeff.liu@...cle.com>
To: Dan Carpenter <dan.carpenter@...cle.com>
CC: Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>,
"David S. Miller" <davem@...emloft.net>, rds-devel@....oracle.com,
netdev@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [patch] RDS: fix an integer overflow check
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@...cle.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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