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authorFlorian Westphal <fw@strlen.de>2020-04-11 21:05:01 +0200
committerDavid S. Miller <davem@davemloft.net>2020-04-12 21:04:08 -0700
commite154659ba39a1c2be576aaa0a5bda8088d707950 (patch)
tree35d3133115483b71105b54d15b5012fbe9ecfe5c /net/mptcp
parent3fe260e00cd0bf0be853c48fcc1e19853df615bb (diff)
mptcp: fix double-unlock in mptcp_poll
mptcp_connect/28740 is trying to release lock (sk_lock-AF_INET) at: [<ffffffff82c15869>] mptcp_poll+0xb9/0x550 but there are no more locks to release! Call Trace: lock_release+0x50f/0x750 release_sock+0x171/0x1b0 mptcp_poll+0xb9/0x550 sock_poll+0x157/0x470 ? get_net_ns+0xb0/0xb0 do_sys_poll+0x63c/0xdd0 Problem is that __mptcp_tcp_fallback() releases the mptcp socket lock, but after recent change it doesn't do this in all of its return paths. To fix this, remove the unlock from __mptcp_tcp_fallback() and always do the unlock in the caller. Also add a small comment as to why we have this __mptcp_needs_tcp_fallback(). Fixes: 0b4f33def7bbde ("mptcp: fix tcp fallback crash") Reported-by: syzbot+e56606435b7bfeea8cf5@syzkaller.appspotmail.com Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/mptcp')
-rw-r--r--net/mptcp/protocol.c25
1 files changed, 13 insertions, 12 deletions
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 939a5045181a..9936e33ac351 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -97,12 +97,7 @@ static struct socket *__mptcp_tcp_fallback(struct mptcp_sock *msk)
if (likely(!__mptcp_needs_tcp_fallback(msk)))
return NULL;
- if (msk->subflow) {
- release_sock((struct sock *)msk);
- return msk->subflow;
- }
-
- return NULL;
+ return msk->subflow;
}
static bool __mptcp_can_create_subflow(const struct mptcp_sock *msk)
@@ -734,9 +729,10 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
goto out;
}
+fallback:
ssock = __mptcp_tcp_fallback(msk);
if (unlikely(ssock)) {
-fallback:
+ release_sock(sk);
pr_debug("fallback passthrough");
ret = sock_sendmsg(ssock, msg);
return ret >= 0 ? ret + copied : (copied ? copied : ret);
@@ -769,8 +765,14 @@ fallback:
if (ret < 0)
break;
if (ret == 0 && unlikely(__mptcp_needs_tcp_fallback(msk))) {
+ /* Can happen for passive sockets:
+ * 3WHS negotiated MPTCP, but first packet after is
+ * plain TCP (e.g. due to middlebox filtering unknown
+ * options).
+ *
+ * Fall back to TCP.
+ */
release_sock(ssk);
- ssock = __mptcp_tcp_fallback(msk);
goto fallback;
}
@@ -883,6 +885,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
ssock = __mptcp_tcp_fallback(msk);
if (unlikely(ssock)) {
fallback:
+ release_sock(sk);
pr_debug("fallback-read subflow=%p",
mptcp_subflow_ctx(ssock->sk));
copied = sock_recvmsg(ssock, msg, flags);
@@ -1467,12 +1470,11 @@ static int mptcp_setsockopt(struct sock *sk, int level, int optname,
*/
lock_sock(sk);
ssock = __mptcp_tcp_fallback(msk);
+ release_sock(sk);
if (ssock)
return tcp_setsockopt(ssock->sk, level, optname, optval,
optlen);
- release_sock(sk);
-
return -EOPNOTSUPP;
}
@@ -1492,12 +1494,11 @@ static int mptcp_getsockopt(struct sock *sk, int level, int optname,
*/
lock_sock(sk);
ssock = __mptcp_tcp_fallback(msk);
+ release_sock(sk);
if (ssock)
return tcp_getsockopt(ssock->sk, level, optname, optval,
option);
- release_sock(sk);
-
return -EOPNOTSUPP;
}