Re: nvme-pci: NULL pointer dereference in nvme_dev_disable() on linux-next

Gerd Bayer
2022-11-08T17:11:24Z

Hi Christoph,

with your minimal fix

On Tue, 2022-11-08 at 08:48 +0100, Christoph Hellwig wrote:
> Below is the minimal fix. I'll see if I sort out the mess that is
> probe/reset failure vs ->remove a bit better, though.
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index f94b05c585cbc..577bacdcfee08 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -5160,6 +5160,8 @@ EXPORT_SYMBOL_GPL(nvme_start_freeze);
>
> void nvme_stop_queues(struct nvme_ctrl *ctrl)
> {
> + if (!ctrl->tagset)
> + return;
> if (!test_and_set_bit(NVME_CTRL_STOPPED, &ctrl->flags))
> blk_mq_quiesce_tagset(ctrl->tagset);
> else
> @@ -5169,6 +5171,8 @@ EXPORT_SYMBOL_GPL(nvme_stop_queues);
>
> void nvme_start_queues(struct nvme_ctrl *ctrl)
> {
> + if (!ctrl->tagset)
> + return;
> if (test_and_clear_bit(NVME_CTRL_STOPPED, &ctrl->flags))
> blk_mq_unquiesce_tagset(ctrl->tagset);
> }

on next-20221108 the kernel does not crash any
more when I run the short test-script.

dmesg shows:
Nov 08 17:38:51 a46lp24.lnxne.boe kernel: nvme nvme0: pci function 0004:00:00.0
Nov 08 17:38:51 a46lp24.lnxne.boe kernel:
nvme nvme0: failed to mark controller CONNECTING
Nov 08 17:38:51 a46lp24.lnxne.boe kernel: nvme nvme0: Removing after
probe failure status: -16
Nov 08 17:38:52 a46lp24.lnxne.boe kernel: pci 0004:00:00.0: Removing from iommu group 0

while kernel remains up.
I can even do
- rescan on the pci bus (to bring back the nvme drive), and
- run the test script
multiple times.

So from my point of view this band-aid is valuable to be incorporated while the larger
overhaul in

https://lore.kernel.org/linux-nvme/20221108150252.2123727-1-hch@lst.de/
is out for review and test.

Feel free to add my
Tested-by: Gerd Bayer <gbayer@linux.ibm.com>

Thank you,
Gerd Bayer