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[net,1/4] mptcp: fix sk_forward_memory corruption on retransmission

Message ID 20210527233140.182728-2-mathew.j.martineau@linux.intel.com
State New, archived
Headers show
Series mptcp: Fixes for 5.13 | expand

Commit Message

Mat Martineau May 27, 2021, 11:31 p.m. UTC
From: Paolo Abeni <pabeni@redhat.com>

MPTCP sk_forward_memory handling is a bit special, as such field
is protected by the msk socket spin_lock, instead of the plain
socket lock.

Currently we have a code path updating such field without handling
the relevant lock:

__mptcp_retrans() -> __mptcp_clean_una_wakeup()

Several helpers in __mptcp_clean_una_wakeup() will update
sk_forward_alloc, possibly causing such field corruption, as reported
by Matthieu.

Address the issue providing and using a new variant of blamed function
which explicitly acquires the msk spin lock.

Fixes: 64b9cea7a0af ("mptcp: fix spurious retransmissions")
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/172
Reported-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Tested-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
 net/mptcp/protocol.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)
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diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 2bc199549a88..5edc686faff1 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -947,6 +947,10 @@  static void __mptcp_update_wmem(struct sock *sk)
 	struct mptcp_sock *msk = mptcp_sk(sk);
+	WARN_ON_ONCE(!lockdep_is_held(&sk->sk_lock.slock));
 	if (!msk->wmem_reserved)
@@ -1085,10 +1089,20 @@  static void __mptcp_clean_una(struct sock *sk)
 static void __mptcp_clean_una_wakeup(struct sock *sk)
+	WARN_ON_ONCE(!lockdep_is_held(&sk->sk_lock.slock));
+static void mptcp_clean_una_wakeup(struct sock *sk)
+	mptcp_data_lock(sk);
+	__mptcp_clean_una_wakeup(sk);
+	mptcp_data_unlock(sk);
 static void mptcp_enter_memory_pressure(struct sock *sk)
 	struct mptcp_subflow_context *subflow;
@@ -2299,7 +2313,7 @@  static void __mptcp_retrans(struct sock *sk)
 	struct sock *ssk;
 	int ret;
-	__mptcp_clean_una_wakeup(sk);
+	mptcp_clean_una_wakeup(sk);
 	dfrag = mptcp_rtx_head(sk);
 	if (!dfrag) {
 		if (mptcp_data_fin_enabled(msk)) {