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Date: Fri, 03 Sep 2010 11:49:10 -0400
From: Vlad Yasevich <vladislav.yasevich@...com>
To: Dan Rosenberg <dan.j.rosenberg@...il.com>
CC: sri@...ibm.com, linux-sctp@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sctp: prevent reading out-of-bounds memory
On 09/03/2010 10:47 AM, Dan Rosenberg wrote:
> Ugh, just remembered the port number is also dereferenced, so the
> second of these two checks needs to be expanded to the size of a
> sockaddr_in. Note to self: don't write patches on too little sleep.
> Apologies for the unnecessary traffic.
>
Actually, you can move that down. Otherwise, we'd end up executing the same code
twice which is just silly.
So, the code should be like this:
1. see if we can get the address family.
2. Get the address family.
3. see if we get the sockaddr of appropriate size,
4. Get that structure.
5. reference fields.
-vlad
> Signed-off-by: Dan Rosenberg <dan.j.rosenberg@...il.com>
>
> --- linux-2.6.35.4.orig/net/sctp/socket.c 2010-09-03 08:58:48.127080114 -0400
> +++ linux-2.6.35.4/net/sctp/socket.c 2010-09-03 10:45:08.467098052 -0400
> @@ -916,6 +916,12 @@ SCTP_STATIC int sctp_setsockopt_bindx(st
> /* Walk through the addrs buffer and count the number of addresses. */
> addr_buf = kaddrs;
> while (walk_size < addrs_size) {
> +
> + if (walk_size + sizeof(sa_family_t) > addrs_size) {
> + kfree(kaddrs);
> + return -EINVAL;
> + }
> +
> sa_addr = (struct sockaddr *)addr_buf;
> af = sctp_get_af_specific(sa_addr->sa_family);
>
> @@ -1002,6 +1008,12 @@ static int __sctp_connect(struct sock* s
> /* Walk through the addrs buffer and count the number of addresses. */
> addr_buf = kaddrs;
> while (walk_size < addrs_size) {
> +
> + if (walk_size + sizeof(struct sockaddr_in) > addrs_size) {
> + err = -EINVAL;
> + goto out_free;
> + }
> +
> sa_addr = (union sctp_addr *)addr_buf;
> af = sctp_get_af_specific(sa_addr->sa.sa_family);
> port = ntohs(sa_addr->v4.sin_port);
>
>
>
> On Fri, Sep 3, 2010 at 10:35 AM, Dan Rosenberg
> <dan.j.rosenberg@...il.com> wrote:
>> Ha, I knew there was an easier way. Take two:
>>
>> Signed-off-by: Dan Rosenberg <dan.j.rosenberg@...il.com>
>>
>> --- linux-2.6.35.4.orig/net/sctp/socket.c 2010-09-03 08:58:48.127080114 -0400
>> +++ linux-2.6.35.4/net/sctp/socket.c 2010-09-03 10:28:14.929595312 -0400
>> @@ -916,6 +916,12 @@ SCTP_STATIC int sctp_setsockopt_bindx(st
>> /* Walk through the addrs buffer and count the number of addresses. */
>> addr_buf = kaddrs;
>> while (walk_size < addrs_size) {
>> +
>> + if (walk_size + sizeof(sa_family_t) > addrs_size) {
>> + kfree(kaddrs);
>> + return -EINVAL;
>> + }
>> +
>> sa_addr = (struct sockaddr *)addr_buf;
>> af = sctp_get_af_specific(sa_addr->sa_family);
>>
>> @@ -1002,6 +1008,12 @@ static int __sctp_connect(struct sock* s
>> /* Walk through the addrs buffer and count the number of addresses. */
>> addr_buf = kaddrs;
>> while (walk_size < addrs_size) {
>> +
>> + if (walk_size + sizeof(sa_family_t) > addrs_size) {
>> + err = -EINVAL;
>> + goto out_free;
>> + }
>> +
>> sa_addr = (union sctp_addr *)addr_buf;
>> af = sctp_get_af_specific(sa_addr->sa.sa_family);
>> port = ntohs(sa_addr->v4.sin_port);
>>
>>
>>>
>>> Hm.. we already validate that we have the proper amount of space for a given sockaddr.
>>> The only thing we are missing is making sure that there is room to get the proper address
>>> family and I think you can do that without adding any extra variables:
>>>
>>> if (walk_size + sizeof(sa_family_t) > addr_size) {
>>> /* Not enough room for address family */
>>> kfree(kaddrs);
>>> return -EINVAL;
>>> }
>>>
>>> -vlad
>>>
>>
>> On Fri, Sep 3, 2010 at 10:15 AM, Vlad Yasevich
>> <vladislav.yasevich@...com> wrote:
>>> On 09/03/2010 09:48 AM, Dan Rosenberg wrote:
>>>> Two user-controlled allocations in SCTP are subsequently dereferenced
>>>> as sockaddr structs, without checking if the dereferenced struct
>>>> members fall beyond the end of the allocated chunk. There doesn't
>>>> appear to be any information leakage here based on how these members
>>>> are used and additional checking, but it's still worth fixing.
>>>>
>>>> Signed-off-by: Dan Rosenberg <dan.j.rosenberg@...il.com>
>>>>
>>>> --- linux-2.6.35.4.orig/net/sctp/socket.c 2010-09-03 08:58:48.127080114 -0400
>>>> +++ linux-2.6.35.4/net/sctp/socket.c 2010-09-03 09:22:06.337096825 -0400
>>>> @@ -889,6 +889,7 @@ SCTP_STATIC int sctp_setsockopt_bindx(st
>>>> int err;
>>>> int addrcnt = 0;
>>>> int walk_size = 0;
>>>> + unsigned int remaining = addrs_size;
>>>> struct sockaddr *sa_addr;
>>>> void *addr_buf;
>>>> struct sctp_af *af;
>>>> @@ -916,6 +917,13 @@ SCTP_STATIC int sctp_setsockopt_bindx(st
>>>> /* Walk through the addrs buffer and count the number of addresses. */
>>>> addr_buf = kaddrs;
>>>> while (walk_size < addrs_size) {
>>>> +
>>>> + /* Don't read out-of-bounds memory */
>>>> + if (remaining < sizeof(struct sockaddr)) {
>>>> + kfree(kaddrs);
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> sa_addr = (struct sockaddr *)addr_buf;
>>>> af = sctp_get_af_specific(sa_addr->sa_family);
>>>>
>>>> @@ -929,6 +937,7 @@ SCTP_STATIC int sctp_setsockopt_bindx(st
>>>> addrcnt++;
>>>> addr_buf += af->sockaddr_len;
>>>> walk_size += af->sockaddr_len;
>>>> + remaining -= af->sockaddr_len;
>>>> }
>>>>
>>>> /* Do the work. */
>>>> @@ -984,6 +993,7 @@ static int __sctp_connect(struct sock* s
>>>> void *addr_buf;
>>>> unsigned short port;
>>>> unsigned int f_flags = 0;
>>>> + unsigned int remaining = addrs_size;
>>>>
>>>> sp = sctp_sk(sk);
>>>> ep = sp->ep;
>>>> @@ -1002,6 +1012,13 @@ static int __sctp_connect(struct sock* s
>>>> /* Walk through the addrs buffer and count the number of addresses. */
>>>> addr_buf = kaddrs;
>>>> while (walk_size < addrs_size) {
>>>> +
>>>> + /* Don't read out-of-bounds memory */
>>>> + if (remaining < sizeof(union sctp_addr)) {
>>>> + err = -EINVAL;
>>>> + goto out_free;
>>>> + }
>>>> +
>>>> sa_addr = (union sctp_addr *)addr_buf;
>>>> af = sctp_get_af_specific(sa_addr->sa.sa_family);
>>>> port = ntohs(sa_addr->v4.sin_port);
>>>> @@ -1101,6 +1118,7 @@ static int __sctp_connect(struct sock* s
>>>> addrcnt++;
>>>> addr_buf += af->sockaddr_len;
>>>> walk_size += af->sockaddr_len;
>>>> + remaining -= af->sockaddr_len;
>>>> }
>>>>
>>>> /* In case the user of sctp_connectx() wants an association
>>>>
>>>
>>>
>>
>
--
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