From: Xin Long Date: Sun, 7 Jun 2026 23:03:47 +0000 (-0400) Subject: sctp: validate embedded INIT chunk and address list lengths in cookie X-Git-Tag: v7.1~17^2~12 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6f4c80a2a7e6d06753b89a578b710a2499a5e62b;p=thirdparty%2Flinux.git sctp: validate embedded INIT chunk and address list lengths in cookie 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 Signed-off-by: Xin Long Link: https://patch.msgid.link/75af23a89adf881a0895d511775e4770da367cbf.1780873427.git.lucien.xin@gmail.com Signed-off-by: Jakub Kicinski --- diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c index 75e3e61d494e0..31737f144c7f0 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 85264862fb6b6..1741a9f33d8c7 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. */