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| author | Sagi Grimberg <sagi@grimberg.me> | 2024-05-27 22:38:52 +0300 |
|---|---|---|
| committer | Keith Busch <kbusch@kernel.org> | 2024-05-28 10:01:52 -0700 |
| commit | c758b77d4a0a0ed3a1292b3fd7a2aeccd1a169a4 (patch) | |
| tree | 305cfc6dc0df555961daaf3879609a4646660f4d /drivers/nvme | |
| parent | be647e2c76b27f409cdd520f66c95be888b553a3 (diff) | |
| download | lwn-c758b77d4a0a0ed3a1292b3fd7a2aeccd1a169a4.tar.gz lwn-c758b77d4a0a0ed3a1292b3fd7a2aeccd1a169a4.zip | |
nvmet: fix a possible leak when destroy a ctrl during qp establishment
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@vastdata.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Diffstat (limited to 'drivers/nvme')
| -rw-r--r-- | drivers/nvme/target/core.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c index 2fde22323622..06f0c587f343 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 |