sctp: validate stream count in sctp_process_strreset_inreq()

Overview

In the Linux kernel, the following vulnerability has been resolved:

sctp: validate stream count in sctp_process_strreset_inreq()

When processing a RESET_IN_REQUEST from a peer, sctp_process_strreset_inreq() derives the stream count from the parameter length but does not check whether the resulting RESET_OUT_REQUEST would exceed SCTP_MAX_CHUNK_LEN.

The OUT request header (sctp_strreset_outreq, 16 bytes) is 8 bytes larger than the IN request header (sctp_strreset_inreq, 8 bytes). Generally, the IP payload is bounded to 65535 bytes, so the stream list cannot be large enough to trigger the overflow. However, on interfaces with MTU > 65535 (e.g., loopback with IPv6 jumbograms), a stream list that fits within the incoming IN parameter can cause a __u16 overflow in sctp_make_strreset_req() when computing the OUT request size, leading to an undersized skb allocation and a kernel BUG:

net/core/skbuff.c:207 skb_panic net/core/skbuff.c:2625 skb_put net/sctp/sm_make_chunk.c:1535 sctp_addto_chunk net/sctp/sm_make_chunk.c:3695 sctp_make_strreset_req net/sctp/stream.c:655 sctp_process_strreset_inreq

The local setsockopt path validates the generated reset request size. However, for an incoming-only reset, it accounts for the smaller IN request even though the peer must generate an OUT request with the same stream list. Such a request cannot be completed successfully by the peer.

Reject peer IN requests whose corresponding OUT request would exceed SCTP_MAX_CHUNK_LEN. Also tighten the local check so it does not send an IN request that would require an oversized OUT request from the peer.

Affected

• Linux >= 7f9d68ac944e24ee5f9ac8d059ca00b1c1d34137 < 61327d8e7cfb0259d527be17202630f556213249
• Linux >= 7f9d68ac944e24ee5f9ac8d059ca00b1c1d34137 < 7cf7439948e3bf639119119922c88ec190874ca3
• Linux >= 7f9d68ac944e24ee5f9ac8d059ca00b1c1d34137 < 60c47dea5d320d2fc706e9aad1db38a04df0a056
• Linux >= 7f9d68ac944e24ee5f9ac8d059ca00b1c1d34137 < b255d8cd6cc68045ae9eecbac3b3c14e1f176c9b
• Linux >= 7f9d68ac944e24ee5f9ac8d059ca00b1c1d34137 < 6f0e39d180cd7cced647381b6fa14fd83d261047
• Linux >= 7f9d68ac944e24ee5f9ac8d059ca00b1c1d34137 < 1a10fe1aa9c01f41b389a31906a77d538637c9d9
• Linux >= 7f9d68ac944e24ee5f9ac8d059ca00b1c1d34137 < 00ae679cb21a035491fdad8d58dc6d79cc68b675
• Linux >= 7f9d68ac944e24ee5f9ac8d059ca00b1c1d34137 < 18ae07691d43183d270de8be9dc8e027906015d9
• Linux 4.11

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.