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Message-ID: <20240605120220.2966127-14-sashal@kernel.org>
Date: Wed, 5 Jun 2024 08:01:57 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Cc: Sagi Grimberg <sagi@...mberg.me>,
Alex Turin <alex@...tdata.com>,
Christoph Hellwig <hch@....de>,
Keith Busch <kbusch@...nel.org>,
Sasha Levin <sashal@...nel.org>,
kch@...dia.com,
linux-nvme@...ts.infradead.org
Subject: [PATCH AUTOSEL 6.9 14/23] nvmet: fix a possible leak when destroy a ctrl during qp establishment
From: Sagi Grimberg <sagi@...mberg.me>
[ Upstream commit c758b77d4a0a0ed3a1292b3fd7a2aeccd1a169a4 ]
In nvmet_sq_destroy we capture sq->ctrl early and if it is non-NULL we
know that a ctrl was allocated (in the admin connect request handler)
and we need to release pending AERs, clear ctrl->sqs and sq->ctrl
(for nvme-loop primarily), and drop the final reference on the ctrl.
However, a small window is possible where nvmet_sq_destroy starts (as
a result of the client giving up and disconnecting) concurrently with
the nvme admin connect cmd (which may be in an early stage). But *before*
kill_and_confirm of sq->ref (i.e. the admin connect managed to get an sq
live reference). In this case, sq->ctrl was allocated however after it was
captured in a local variable in nvmet_sq_destroy.
This prevented the final reference drop on the ctrl.
Solve this by re-capturing the sq->ctrl after all inflight request has
completed, where for sure sq->ctrl reference is final, and move forward
based on that.
This issue was observed in an environment with many hosts connecting
multiple ctrls simoutanuosly, creating a delay in allocating a ctrl
leading up to this race window.
Reported-by: Alex Turin <alex@...tdata.com>
Signed-off-by: Sagi Grimberg <sagi@...mberg.me>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Keith Busch <kbusch@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
drivers/nvme/target/core.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 2fde22323622e..06f0c587f3437 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -818,6 +818,15 @@ void nvmet_sq_destroy(struct nvmet_sq *sq)
percpu_ref_exit(&sq->ref);
nvmet_auth_sq_free(sq);
+ /*
+ * we must reference the ctrl again after waiting for inflight IO
+ * to complete. Because admin connect may have sneaked in after we
+ * store sq->ctrl locally, but before we killed the percpu_ref. the
+ * admin connect allocates and assigns sq->ctrl, which now needs a
+ * final ref put, as this ctrl is going away.
+ */
+ ctrl = sq->ctrl;
+
if (ctrl) {
/*
* The teardown flow may take some time, and the host may not
--
2.43.0
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