This is a note to let you know that I've just added the patch titled
[PATCH-stable] nvme: Fix memory order on async queue deletion
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: nvme-fix-memory-order-on-async-queue-deletion.patch and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From keith.busch@intel.com Tue Nov 21 17:57:03 2017
From: Keith Busch keith.busch@intel.com Date: Thu, 16 Nov 2017 16:57:10 -0700 Subject: [PATCH-stable] nvme: Fix memory order on async queue deletion To: linux-nvme@lists.infradead.org, stable@vger.kernel.org Cc: Greg KH gregkh@linuxfoundation.org, Keith Busch keith.busch@intel.com Message-ID: 20171116235710.20224-1-keith.busch@intel.com
From: Keith Busch keith.busch@intel.com
This patch is a fix specific to the 3.19 - 4.4 kernels. The 4.5 kernel inadvertently fixed this bug differently (db3cbfff5bcc0), but is not a stable candidate due it being a complicated re-write of the entire feature.
This patch fixes a potential timing bug with nvme's asynchronous queue deletion, which causes an allocated request to be accidentally released due to the ordering of the shared completion context among the sq/cq pair. The completion context saves the request that issued the queue deletion. If the submission side deletion happens to reset the active request, the completion side will release the wrong request tag back into the pool of available tags. This means the driver will create multiple commands with the same tag, corrupting the queue context.
The error is observable in the kernel logs like:
"nvme XX:YY:ZZ completed id XX twice on qid:0"
In this particular case, this message occurs because the queue is corrupted.
The following timing sequence demonstrates the error:
CPU A CPU B ----------------------- ----------------------------- nvme_irq nvme_process_cq async_completion queue_kthread_work -----------> nvme_del_sq_work_handler nvme_delete_cq adapter_async_del_queue nvme_submit_admin_async_cmd cmdinfo->req = req;
blk_mq_free_request(cmdinfo->req); <-- wrong request!!!
This patch fixes the bug by releasing the request in the completion side prior to waking the submission thread, such that that thread can't muck with the shared completion context.
Fixes: a4aea5623d4a5 ("NVMe: Convert to blk-mq")
Signed-off-by: Keith Busch keith.busch@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/nvme/host/pci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -350,8 +350,8 @@ static void async_completion(struct nvme struct async_cmd_info *cmdinfo = ctx; cmdinfo->result = le32_to_cpup(&cqe->result); cmdinfo->status = le16_to_cpup(&cqe->status) >> 1; - queue_kthread_work(cmdinfo->worker, &cmdinfo->work); blk_mq_free_request(cmdinfo->req); + queue_kthread_work(cmdinfo->worker, &cmdinfo->work); }
static inline struct nvme_cmd_info *get_cmd_from_tag(struct nvme_queue *nvmeq,
Patches currently in stable-queue which might be from keith.busch@intel.com are
queue-4.4/nvme-fix-memory-order-on-async-queue-deletion.patch