Vulnerability CVE-2024-42152
Published: 2024-07-30

Description:
In the Linux kernel, the following vulnerability has been resolved:

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.

 References:
https://git.kernel.org/stable/c/2f3c22b1d3d7e86712253244797a651998c141fa
https://git.kernel.org/stable/c/b4fed1443a6571d49c6ffe7d97af3bbe5ee6dff5
https://git.kernel.org/stable/c/940a71f08ef153ef807f751310b0648d1fa5d0da
https://git.kernel.org/stable/c/5502c1f1d0d7472706cc1f201aecf1c935d302d1
https://git.kernel.org/stable/c/818004f2a380420c19872171be716174d4985e33
https://git.kernel.org/stable/c/c758b77d4a0a0ed3a1292b3fd7a2aeccd1a169a4
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