sctp: trim optlen when it's a huge value in sctp_setsockopt

After commit ca84bd058dae ("sctp: copy the optval from user space in
sctp_setsockopt"), it does memory allocation in sctp_setsockopt with
the optlen, and it would fail the allocation and return error if the
optlen from user space is a huge value.

This breaks some sockopts, like SCTP_HMAC_IDENT, SCTP_RESET_STREAMS and
SCTP_AUTH_KEY, as when processing these sockopts before, optlen would
be trimmed to a biggest value it needs when optlen is a huge value,
instead of failing the allocation and returning error.

This patch is to fix the allocation failure when it's a huge optlen from
user space by trimming it to the biggest size sctp sockopt may need when
necessary, and this biggest size is from sctp_setsockopt_reset_streams()
for SCTP_RESET_STREAMS, which is bigger than those for SCTP_HMAC_IDENT
and SCTP_AUTH_KEY.

Fixes: ca84bd058dae ("sctp: copy the optval from user space in sctp_setsockopt")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index e64e01f61b117b8befe206d1eb4807d96aad09b4..6b937bfd475159df6b15e6a30023e30f09ff0a07 100644 (file)
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4577,6 +4577,10 @@ static int sctp_setsockopt(struct sock *sk, int level, int optname,
        }
 
        if (optlen > 0) {
+               /* Trim it to the biggest size sctp sockopt may need if necessary */
+               optlen = min_t(unsigned int, optlen,
+                              PAGE_ALIGN(USHRT_MAX +
+                                         sizeof(__u16) * sizeof(struct sctp_reset_streams)));
                kopt = memdup_sockptr(optval, optlen);
                if (IS_ERR(kopt))
                        return PTR_ERR(kopt);