[PATCH 5.11 156/210] mptcp: forbit mcast-related sockopt on MPTCP sockets

Greg Kroah-Hartman
2021-04-12T09:36:05Z

From: Paolo Abeni <pabeni@redhat.com>

[ Upstream commit 86581852d7710990d8af9dadfe9a661f0abf2114 ]

Unrolling mcast state at msk dismantel time is bug prone, as
syzkaller reported:

======================================================
WARNING: possible circular locking dependency detected
5.11.0-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor905/8822 is trying to acquire lock:
ffffffff8d678fe8 (rtnl_mutex){+.+.}-{3:3}, at: ipv6_sock_mc_close+0xd7/0x110 net/ipv6/mcast.c:323

but task is already holding lock:
ffff888024390120 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1600 [inline]
ffff888024390120 (sk_lock-AF_INET6){+.+.}-{0:0}, at: mptcp6_release+0x57/0x130 net/mptcp/protocol.c:3507

which lock already depends on the new lock.

Instead we can simply forbit any mcast-related setsockopt

Fixes: 717e79c867ca5 ("mptcp: Add setsockopt()/getsockopt() socket operations")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/mptcp/protocol.c | 45 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 5932b0ebecc3..de9f2509acbe 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2863,6 +2863,48 @@ static int mptcp_setsockopt_v6(struct mptcp_sock *msk, int optname,
return ret;
}

+static bool mptcp_unsupported(int level, int optname)
+{
+ if (level == SOL_IP) {
+ switch (optname) {
+ case IP_ADD_MEMBERSHIP:
+ case IP_ADD_SOURCE_MEMBERSHIP:
+ case IP_DROP_MEMBERSHIP:
+ case IP_DROP_SOURCE_MEMBERSHIP:
+ case IP_BLOCK_SOURCE:
+ case IP_UNBLOCK_SOURCE:
+ case MCAST_JOIN_GROUP:
+ case MCAST_LEAVE_GROUP:
+ case MCAST_JOIN_SOURCE_GROUP:
+ case MCAST_LEAVE_SOURCE_GROUP:
+ case MCAST_BLOCK_SOURCE:
+ case MCAST_UNBLOCK_SOURCE:
+ case MCAST_MSFILTER:
+ return true;
+ }
+ return false;
+ }
+ if (level == SOL_IPV6) {
+ switch (optname) {
+ case IPV6_ADDRFORM:
+ case IPV6_ADD_MEMBERSHIP:
+ case IPV6_DROP_MEMBERSHIP:
+ case IPV6_JOIN_ANYCAST:
+ case IPV6_LEAVE_ANYCAST:
+ case MCAST_JOIN_GROUP:
+ case MCAST_LEAVE_GROUP:
+ case MCAST_JOIN_SOURCE_GROUP:
+ case MCAST_LEAVE_SOURCE_GROUP:
+ case MCAST_BLOCK_SOURCE:
+ case MCAST_UNBLOCK_SOURCE:
+ case MCAST_MSFILTER:
+ return true;
+ }
+ return false;
+ }
+ return false;
+}
+
static int mptcp_setsockopt(struct sock *sk, int level, int optname,
sockptr_t optval, unsigned int optlen)
{
@@ -2871,6 +2913,9 @@ static int mptcp_setsockopt(struct sock *sk, int level, int optname,

pr_debug("msk=%p", msk);

+ if (mptcp_unsupported(level, optname))
+ return -ENOPROTOOPT;
+
if (level == SOL_SOCKET)
return mptcp_setsockopt_sol_socket(msk, optname, optval, optlen);

--
2.30.2