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mptcp: fix race in release_cb

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If we receive a MPTCP_PUSH_PENDING even from a subflow when
mptcp_release_cb() is serving the previous one, the latter
will be delayed up to the next release_sock(msk).

Address the issue implementing a test/serve loop for such
event.

Additionally rename the push helper to __mptcp_push_pending()
to be more consistent with the existing code.

Fixes: 6e628cd3a8 ("mptcp: use mptcp release_cb for delayed tasks")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2021-03-04 13:32:14 -08:00 • committed by David S. Miller
parent 2948d0a1e5
commit c2e6048fa1
1 changed files with 21 additions and 12 deletions
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33
net/mptcp/protocol.c
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@ -1445,7 +1445,7 @@ static void mptcp_push_release(struct sock *sk, struct sock *ssk,
release_sock(ssk); release_sock(ssk);
} }
static void mptcp_push_pending(struct sock *sk, unsigned int flags) static void __mptcp_push_pending(struct sock *sk, unsigned int flags)
{ {
struct sock *prev_ssk = NULL, *ssk = NULL; struct sock *prev_ssk = NULL, *ssk = NULL;
struct mptcp_sock *msk = mptcp_sk(sk); struct mptcp_sock *msk = mptcp_sk(sk);
@ -1697,14 +1697,14 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
wait_for_memory: wait_for_memory:
mptcp_set_nospace(sk); mptcp_set_nospace(sk);
mptcp_push_pending(sk, msg->msg_flags); __mptcp_push_pending(sk, msg->msg_flags);
ret = sk_stream_wait_memory(sk, &timeo); ret = sk_stream_wait_memory(sk, &timeo);
if (ret) if (ret)
goto out; goto out;
} }
if (copied) if (copied)
mptcp_push_pending(sk, msg->msg_flags); __mptcp_push_pending(sk, msg->msg_flags);
out: out:
release_sock(sk); release_sock(sk);
@ -2959,13 +2959,14 @@ static void mptcp_release_cb(struct sock *sk)
{ {
unsigned long flags, nflags; unsigned long flags, nflags;
/* push_pending may touch wmem_reserved, do it before the later for (;;) {
* cleanup flags = 0;
*/ if (test_and_clear_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->flags))
if (test_and_clear_bit(MPTCP_CLEAN_UNA, &mptcp_sk(sk)->flags)) flags |= MPTCP_PUSH_PENDING;
__mptcp_clean_una(sk); if (!flags)
if (test_and_clear_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->flags)) { break;
/* mptcp_push_pending() acquires the subflow socket lock
/* the following actions acquire the subflow socket lock
* *
* 1) can't be invoked in atomic scope * 1) can't be invoked in atomic scope
* 2) must avoid ABBA deadlock with msk socket spinlock: the RX * 2) must avoid ABBA deadlock with msk socket spinlock: the RX
@ -2974,13 +2975,21 @@ static void mptcp_release_cb(struct sock *sk)
*/ */
spin_unlock_bh(&sk->sk_lock.slock); spin_unlock_bh(&sk->sk_lock.slock);
mptcp_push_pending(sk, 0); if (flags & MPTCP_PUSH_PENDING)
__mptcp_push_pending(sk, 0);
cond_resched();
spin_lock_bh(&sk->sk_lock.slock); spin_lock_bh(&sk->sk_lock.slock);
} }
if (test_and_clear_bit(MPTCP_CLEAN_UNA, &mptcp_sk(sk)->flags))
__mptcp_clean_una(sk);
if (test_and_clear_bit(MPTCP_ERROR_REPORT, &mptcp_sk(sk)->flags)) if (test_and_clear_bit(MPTCP_ERROR_REPORT, &mptcp_sk(sk)->flags))
__mptcp_error_report(sk); __mptcp_error_report(sk);
/* clear any wmem reservation and errors */ /* push_pending may touch wmem_reserved, ensure we do the cleanup
* later
*/
__mptcp_update_wmem(sk); __mptcp_update_wmem(sk);
__mptcp_update_rmem(sk); __mptcp_update_rmem(sk);