sctp_unpack_cookie() only checked that the embedded INIT chunk length
did not exceed the remaining cookie payload, but did not ensure that the
INIT chunk is large enough to contain a complete INIT header.

A malformed COOKIE_ECHO can therefore carry a truncated INIT chunk whose
length field is smaller than sizeof(struct sctp_init_chunk).  Later,
sctp_process_init() accesses INIT parameters unconditionally, which may
lead to out-of-bounds reads.

In addition, raw_addr_list_len is not fully validated against the
remaining cookie payload. When cookie authentication is disabled, an
attacker can supply an oversized raw_addr_list_len and cause
sctp_raw_to_bind_addrs() to read beyond the end of the cookie. The
address parser also lacks sufficient bounds checks for parameter headers
and lengths, allowing malformed address parameters to trigger
out-of-bounds reads.

Fix this by:

- requiring the embedded INIT chunk length to be at least sizeof(struct
  sctp_init_chunk);
- validating that the INIT chunk and raw address list together fit
  within the cookie payload;
- verifying sufficient data exists for each address parameter header and
  payload before parsing it.

Note that sctp_verify_init() must be called after sctp_unpack_cookie()
and before sctp_process_init() when cookie authentication is disabled.
This will be addressed in a separate patch.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 net/sctp/bind_addr.c     | 11 ++++++++++-
 net/sctp/sm_make_chunk.c |  9 +++++++--
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
index 75e3e61d494e..31737f144c7f 100644
--- a/net/sctp/bind_addr.c
+++ b/net/sctp/bind_addr.c

@@ -275,6 +275,16 @@ int sctp_raw_to_bind_addrs(struct sctp_bind_addr *bp, __u8 *raw_addr_list,
                param = (struct sctp_paramhdr *)raw_addr_list;
                rawaddr = (union sctp_addr_param *)raw_addr_list;

+               if (addrs_len < sizeof(*param)) {
+                       retval = -EINVAL;
+                       goto out_err;
+               }
+               len = ntohs(param->length);
+               if (addrs_len < len) {
+                       retval = -EINVAL;
+                       goto out_err;
+               }
+
                af = sctp_get_af_specific(param_type2af(param->type));
                if (unlikely(!af) ||
                    !af->from_addr_param(&addr, rawaddr, htons(port), 0)) {

@@ -291,7 +301,6 @@ int sctp_raw_to_bind_addrs(struct sctp_bind_addr *bp, __u8 *raw_addr_list,
                        goto out_err;

 next:
-               len = ntohs(param->length);
                addrs_len -= len;
                raw_addr_list += len;
        }

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 85264862fb6b..1741a9f33d8c 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c

@@ -1731,8 +1731,8 @@ struct sctp_association *sctp_unpack_cookie(
        struct sk_buff *skb = chunk->skb;
        struct sctp_cookie *bear_cookie;
        struct sctp_chunkhdr *ch;
+       unsigned int len, chlen;
        enum sctp_scope scope;
-       unsigned int len;
        ktime_t kt;

        /* Header size is static data prior to the actual cookie, including

@@ -1761,7 +1761,12 @@ struct sctp_association *sctp_unpack_cookie(
        bear_cookie = &cookie->c;

        ch = (struct sctp_chunkhdr *)(bear_cookie + 1);
-       if (ntohs(ch->length) > len - fixed_size)
+       chlen = ntohs(ch->length);
+       if (chlen < sizeof(struct sctp_init_chunk))
+               goto malformed;
+       if (chlen > len - fixed_size)
+               goto malformed;
+       if (bear_cookie->raw_addr_list_len > len - fixed_size - chlen)
                goto malformed;

        /* Verify the cookie's MAC, if cookie authentication is enabled. */
--

2.47.1