[v2] netfilter: ipset: Fix overflow before widen in the bitmap_ip_create() function.

[PATCH v2] netfilter: ipset: Fix overflow before widen in the bitmap_ip_create() function.

Posted by Gavrilov Ilia 2 years, 8 months ago

When first_ip is 0, last_ip is 0xFFFFFFFF, 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.

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@infotecs.ru>
---
v2: Fix typo of the last_ip value in the description. Fix the expression for 'hosts'.
 net/netfilter/ipset/ip_set_bitmap_ip.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/ipset/ip_set_bitmap_ip.c b/net/netfilter/ipset/ip_set_bitmap_ip.c
index a8ce04a4bb72..e4fa00abde6a 100644
--- a/net/netfilter/ipset/ip_set_bitmap_ip.c
+++ b/net/netfilter/ipset/ip_set_bitmap_ip.c
@@ -308,8 +308,8 @@ bitmap_ip_create(struct net *net, struct ip_set *set, struct nlattr *tb[],
 			return -IPSET_ERR_BITMAP_RANGE;
 
 		pr_debug("mask_bits %u, netmask %u\n", mask_bits, netmask);
-		hosts = 2 << (32 - netmask - 1);
-		elements = 2 << (netmask - mask_bits - 1);
+		hosts = 2U << (32 - netmask - 1);
+		elements = 2UL << (netmask - mask_bits - 1);
 	}
 	if (elements > IPSET_BITMAP_MAX_RANGE + 1)
 		return -IPSET_ERR_BITMAP_RANGE_SIZE;
-- 
2.30.2

Re: [PATCH v2] netfilter: ipset: Fix overflow before widen in the bitmap_ip_create() function.

Posted by Simon Horman 2 years, 8 months ago

On Wed, Jan 11, 2023 at 11:57:39AM +0000, Gavrilov Ilia wrote:
> [You don't often get email from ilia.gavrilov@infotecs.ru. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> When first_ip is 0, last_ip is 0xFFFFFFFF, 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.
> 
> 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@infotecs.ru>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

> ---
> v2: Fix typo of the last_ip value in the description. Fix the expression for 'hosts'.
>  net/netfilter/ipset/ip_set_bitmap_ip.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/ipset/ip_set_bitmap_ip.c b/net/netfilter/ipset/ip_set_bitmap_ip.c
> index a8ce04a4bb72..e4fa00abde6a 100644
> --- a/net/netfilter/ipset/ip_set_bitmap_ip.c
> +++ b/net/netfilter/ipset/ip_set_bitmap_ip.c
> @@ -308,8 +308,8 @@ bitmap_ip_create(struct net *net, struct ip_set *set, struct nlattr *tb[],
>                         return -IPSET_ERR_BITMAP_RANGE;
> 
>                 pr_debug("mask_bits %u, netmask %u\n", mask_bits, netmask);
> -               hosts = 2 << (32 - netmask - 1);
> -               elements = 2 << (netmask - mask_bits - 1);
> +               hosts = 2U << (32 - netmask - 1);
> +               elements = 2UL << (netmask - mask_bits - 1);
>         }
>         if (elements > IPSET_BITMAP_MAX_RANGE + 1)
>                 return -IPSET_ERR_BITMAP_RANGE_SIZE;
> --
> 2.30.2

Re: [PATCH v2] netfilter: ipset: Fix overflow before widen in the bitmap_ip_create() function.

Posted by Pablo Neira Ayuso 2 years, 8 months ago

On Wed, Jan 11, 2023 at 01:00:53PM +0100, Simon Horman wrote:
> On Wed, Jan 11, 2023 at 11:57:39AM +0000, Gavrilov Ilia wrote:
> > [You don't often get email from ilia.gavrilov@infotecs.ru. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> > 
> > When first_ip is 0, last_ip is 0xFFFFFFFF, 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.
> > 
> > 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@infotecs.ru>
> 
> Reviewed-by: Simon Horman <simon.horman@corigine.com>

Applied, thanks