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Message-ID: <Y76NQ7tQVB7kE0dG@corigine.com>
Date: Wed, 11 Jan 2023 11:19:47 +0100
From: Simon Horman <simon.horman@...igine.com>
To: Gavrilov Ilia <Ilia.Gavrilov@...otecs.ru>
Cc: Pablo Neira Ayuso <pablo@...filter.org>,
Jozsef Kadlecsik <kadlec@...filter.org>,
Florian Westphal <fw@...len.de>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
"netfilter-devel@...r.kernel.org" <netfilter-devel@...r.kernel.org>,
"coreteam@...filter.org" <coreteam@...filter.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"lvc-project@...uxtesting.org" <lvc-project@...uxtesting.org>
Subject: Re: [PATCH] netfilter: ipset: Fix overflow before widen in the
bitmap_ip_create() function.
Hi Gavrilov,
On Mon, Jan 09, 2023 at 11:54:02AM +0000, Gavrilov Ilia wrote:
> When first_ip is 0, last_ip is 0xFFFFFFF, and netmask is 31, the value of
> an arithmetic expression 2 << (netmask - mask_bits - 1) is subject
> to overflow due to a failure casting operands to a larger data type
> before performing the arithmetic.
>
> Note that it's harmless since the value will be checked at the next step.
Do you mean 0xFFFFFFFF (8 rather than 8 'F's) ?
If so, I agree with this patch.
> Found by InfoTeCS on behalf of Linux Verification Center
> (linuxtesting.org) with SVACE.
>
> Fixes: b9fed748185a ("netfilter: ipset: Check and reject crazy /0 input parameters")
> Signed-off-by: Ilia.Gavrilov <Ilia.Gavrilov@...otecs.ru>
> ---
> net/netfilter/ipset/ip_set_bitmap_ip.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/netfilter/ipset/ip_set_bitmap_ip.c b/net/netfilter/ipset/ip_set_bitmap_ip.c
> index a8ce04a4bb72..b8f0fb37378f 100644
> --- a/net/netfilter/ipset/ip_set_bitmap_ip.c
> +++ b/net/netfilter/ipset/ip_set_bitmap_ip.c
> @@ -309,7 +309,7 @@ bitmap_ip_create(struct net *net, struct ip_set *set, struct nlattr *tb[],
>
> pr_debug("mask_bits %u, netmask %u\n", mask_bits, netmask);
> hosts = 2 << (32 - netmask - 1);
I think that hosts also overflows, in the case you have described.
Although it also doesn't matter for the same reason you state.
But from a correctness point of view perhaps it should also be addressed?
> - elements = 2 << (netmask - mask_bits - 1);
> + elements = 2UL << (netmask - mask_bits - 1);
> }
> if (elements > IPSET_BITMAP_MAX_RANGE + 1)
> return -IPSET_ERR_BITMAP_RANGE_SIZE;
> --
> 2.30.2
>
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