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mptcp: fix data re-injection from stale subflow

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When the MPTCP PM detects that a subflow is stale, all the packet
scheduler must re-inject all the mptcp-level unacked data. To avoid
acquiring unneeded locks, it first try to check if any unacked data
is present at all in the RTX queue, but such check is currently
broken, as it uses TCP-specific helper on an MPTCP socket.

Funnily enough fuzzers and static checkers are happy, as the accessed
memory still belongs to the mptcp_sock struct, and even from a
functional perspective the recovery completed successfully, as
the short-cut test always failed.

A recent unrelated TCP change - commit d5fed5addb ("tcp: reorganize
tcp_sock fast path variables") - exposed the issue, as the tcp field
reorganization makes the mptcp code always skip the re-inection.

Fix the issue dropping the bogus call: we are on a slow path, the early
optimization proved once again to be evil.

Fixes: 1e1d9d6f11 ("mptcp: handle pending data on closed subflow")
Cc: stable@vger.kernel.org
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/468
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240131-upstream-net-20240131-mptcp-ci-issues-v1-1-4c1c11e571ff@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Paolo Abeni 2024-01-31 22:49:46 +01:00 committed by Jakub Kicinski
parent c15a729c9d
commit b6c620dc43
1 changed files with 0 additions and 3 deletions
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3
net/mptcp/protocol.c
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@ -2314,9 +2314,6 @@ bool __mptcp_retransmit_pending_data(struct sock *sk)
if (__mptcp_check_fallback(msk)) if (__mptcp_check_fallback(msk))
return false; return false;
if (tcp_rtx_and_write_queues_empty(sk))
return false;
/* the closing socket has some data untransmitted and/or unacked: /* the closing socket has some data untransmitted and/or unacked:
* some data in the mptcp rtx queue has not really xmitted yet. * some data in the mptcp rtx queue has not really xmitted yet.
* keep it simple and re-inject the whole mptcp level rtx queue * keep it simple and re-inject the whole mptcp level rtx queue