4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Xin Long lucien.xin@gmail.com
[ Upstream commit c5006b8aa74599ce19104b31d322d2ea9ff887cc ]
The check in sctp_sockaddr_af is not robust enough to forbid binding a v4mapped v6 addr on a v4 socket.
The worse thing is that v4 socket's bind_verify would not convert this v4mapped v6 addr to a v4 addr. syzbot even reported a crash as the v4 socket bound a v6 addr.
This patch is to fix it by doing the common sa.sa_family check first, then AF_INET check for v4mapped v6 addrs.
Fixes: 7dab83de50c7 ("sctp: Support ipv6only AF_INET6 sockets.") Reported-by: syzbot+7b7b518b1228d2743963@syzkaller.appspotmail.com Acked-by: Neil Horman nhorman@tuxdriver.com Signed-off-by: Xin Long lucien.xin@gmail.com Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sctp/socket.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-)
--- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -332,16 +332,14 @@ static struct sctp_af *sctp_sockaddr_af( if (len < sizeof (struct sockaddr)) return NULL;
+ if (!opt->pf->af_supported(addr->sa.sa_family, opt)) + return NULL; + /* V4 mapped address are really of AF_INET family */ if (addr->sa.sa_family == AF_INET6 && - ipv6_addr_v4mapped(&addr->v6.sin6_addr)) { - if (!opt->pf->af_supported(AF_INET, opt)) - return NULL; - } else { - /* Does this PF support this AF? */ - if (!opt->pf->af_supported(addr->sa.sa_family, opt)) - return NULL; - } + ipv6_addr_v4mapped(&addr->v6.sin6_addr) && + !opt->pf->af_supported(AF_INET, opt)) + return NULL;
/* If we get this far, af is valid. */ af = sctp_get_af_specific(addr->sa.sa_family);