Re: [PATCH] sctp: prevent reading out-of-bounds memory
From: Dan Rosenberg
Date: Fri Sep 03 2010 - 10:47:49 EST
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.
Signed-off-by: Dan Rosenberg <dan.j.rosenberg@xxxxxxxxx>
--- 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@xxxxxxxxx> wrote:
> Ha, I knew there was an easier way. Take two:
>
> Signed-off-by: Dan Rosenberg <dan.j.rosenberg@xxxxxxxxx>
>
> --- 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@xxxxxx> 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@xxxxxxxxx>
>>>
>>> --- 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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