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sctp: validate embedded INIT chunk and address list lengths in cookie

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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: 1da177e4c3 ("Linux-2.6.12-rc2")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/75af23a89adf881a0895d511775e4770da367cbf.1780873427.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Xin Long 2026-06-07 19:03:47 -04:00 • committed by Jakub Kicinski
commit 6f4c80a2a7
2 changed files with 17 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

11
net/sctp/bind_addr.c
View file

@ -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;
}

9
net/sctp/sm_make_chunk.c
View file

@ -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. */