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@xxxxxxxxxxxxxxxxxxxxxxxxx
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
---
net/sctp/socket.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index feb2ca6..039fcb6 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -335,16 +335,14 @@ static struct sctp_af *sctp_sockaddr_af(struct sctp_sock *opt,
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);
--
2.1.0
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