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    Subject[PATCH 5.4 033/309] nvmet: Fix controller use after free
    Date
    From: Israel Rukshin <israelr@mellanox.com>

    commit 1a3f540d63152b8db0a12de508bfa03776217d83 upstream.

    After nvmet_install_queue() sets sq->ctrl calling to nvmet_sq_destroy()
    reduces the controller refcount. In case nvmet_install_queue() fails,
    calling to nvmet_ctrl_put() is done twice (at nvmet_sq_destroy and
    nvmet_execute_io_connect/nvmet_execute_admin_connect) instead of once for
    the queue which leads to use after free of the controller. Fix this by set
    NULL at sq->ctrl in case of a failure at nvmet_install_queue().

    The bug leads to the following Call Trace:

    [65857.994862] refcount_t: underflow; use-after-free.
    [65858.108304] Workqueue: events nvmet_rdma_release_queue_work [nvmet_rdma]
    [65858.115557] RIP: 0010:refcount_warn_saturate+0xe5/0xf0
    [65858.208141] Call Trace:
    [65858.211203] nvmet_sq_destroy+0xe1/0xf0 [nvmet]
    [65858.216383] nvmet_rdma_release_queue_work+0x37/0xf0 [nvmet_rdma]
    [65858.223117] process_one_work+0x167/0x370
    [65858.227776] worker_thread+0x49/0x3e0
    [65858.232089] kthread+0xf5/0x130
    [65858.235895] ? max_active_store+0x80/0x80
    [65858.240504] ? kthread_bind+0x10/0x10
    [65858.244832] ret_from_fork+0x1f/0x30
    [65858.249074] ---[ end trace f82d59250b54beb7 ]---

    Fixes: bb1cc74790eb ("nvmet: implement valid sqhd values in completions")
    Fixes: 1672ddb8d691 ("nvmet: Add install_queue callout")
    Signed-off-by: Israel Rukshin <israelr@mellanox.com>
    Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Keith Busch <kbusch@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/nvme/target/fabrics-cmd.c | 13 +++++++++----
    1 file changed, 9 insertions(+), 4 deletions(-)

    --- a/drivers/nvme/target/fabrics-cmd.c
    +++ b/drivers/nvme/target/fabrics-cmd.c
    @@ -105,6 +105,7 @@ static u16 nvmet_install_queue(struct nv
    u16 qid = le16_to_cpu(c->qid);
    u16 sqsize = le16_to_cpu(c->sqsize);
    struct nvmet_ctrl *old;
    + u16 ret;

    old = cmpxchg(&req->sq->ctrl, NULL, ctrl);
    if (old) {
    @@ -115,7 +116,8 @@ static u16 nvmet_install_queue(struct nv
    if (!sqsize) {
    pr_warn("queue size zero!\n");
    req->error_loc = offsetof(struct nvmf_connect_command, sqsize);
    - return NVME_SC_CONNECT_INVALID_PARAM | NVME_SC_DNR;
    + ret = NVME_SC_CONNECT_INVALID_PARAM | NVME_SC_DNR;
    + goto err;
    }

    /* note: convert queue size from 0's-based value to 1's-based value */
    @@ -128,16 +130,19 @@ static u16 nvmet_install_queue(struct nv
    }

    if (ctrl->ops->install_queue) {
    - u16 ret = ctrl->ops->install_queue(req->sq);
    -
    + ret = ctrl->ops->install_queue(req->sq);
    if (ret) {
    pr_err("failed to install queue %d cntlid %d ret %x\n",
    qid, ctrl->cntlid, ret);
    - return ret;
    + goto err;
    }
    }

    return 0;
    +
    +err:
    + req->sq->ctrl = NULL;
    + return ret;
    }

    static void nvmet_execute_admin_connect(struct nvmet_req *req)

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