diff options
| author | Paolo Abeni <pabeni@redhat.com> | 2023-03-09 15:49:57 +0100 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2023-03-10 21:42:56 -0800 |
| commit | b7a679ba7c652587b85294f4953f33ac0b756d40 (patch) | |
| tree | 726eb073c3ce555b940826bf4e9c28dd177fdd6d /net | |
| parent | 12508b3eb69e2c13e82bbc746ec74b6fcaf33fd4 (diff) | |
mptcp: fix possible deadlock in subflow_error_report
Christoph reported a possible deadlock while the TCP stack
destroys an unaccepted subflow due to an incoming reset: the
MPTCP socket error path tries to acquire the msk-level socket
lock while TCP still owns the listener socket accept queue
spinlock, and the reverse dependency already exists in the
TCP stack.
Note that the above is actually a lockdep false positive, as
the chain involves two separate sockets. A different per-socket
lockdep key will address the issue, but such a change will be
quite invasive.
Instead, we can simply stop earlier the socket error handling
for orphaned or unaccepted subflows, breaking the critical
lockdep chain. Error handling in such a scenario is a no-op.
Reported-and-tested-by: Christoph Paasch <cpaasch@apple.com>
Fixes: 15cc10453398 ("mptcp: deliver ssk errors to msk")
Cc: stable@vger.kernel.org
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/355
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/mptcp/subflow.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 4ae1a7304cf0..5070dc33675d 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1432,6 +1432,13 @@ static void subflow_error_report(struct sock *ssk) { struct sock *sk = mptcp_subflow_ctx(ssk)->conn; + /* bail early if this is a no-op, so that we avoid introducing a + * problematic lockdep dependency between TCP accept queue lock + * and msk socket spinlock + */ + if (!sk->sk_socket) + return; + mptcp_data_lock(sk); if (!sock_owned_by_user(sk)) __mptcp_error_report(sk); |