Re: [PATCH 1/1] nvme: fix use-after-free of admin queue via stale pointer

[Ming Lei <ming.lei@redhat.com>]

On Wed, Oct 29, 2025 at 11:00:29PM +0000, Chaitanya Kulkarni wrote:
> On 10/29/25 2:08 PM, Casey Chen wrote:
> > From: Yuanyuan Zhong <yzhong@purestorage.com>
> >
> > When a controller is deleted (e.g., via sysfs delete_controller), the
> > admin queue is freed while userspace may still have open fd to the
> > namespace block device. Userspace can issue IOCTLs on the open fd
> > that access the freed admin queue through the stale ns->ctrl->admin_q
> > pointer, causing a use-after-free.
> >
> > Fix this by taking an additional reference on the admin queue during
> > namespace allocation and releasing it during namespace cleanup.
> >
> > Signed-off-by: Casey Chen <cachen@purestorage.com>
> > Signed-off-by: Seamus Connor <sconnor@purestorage.com>
> > ---
> >   drivers/nvme/host/core.c | 10 +++++++++-
> >   1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> > index 8d8af58e79d1..184a6096a2be 100644
> > --- a/drivers/nvme/host/core.c
> > +++ b/drivers/nvme/host/core.c
> > @@ -687,6 +687,7 @@ static void nvme_free_ns(struct kref *kref)
> >   {
> >   	struct nvme_ns *ns = container_of(kref, struct nvme_ns, kref);
> >   
> > +	blk_put_queue(ns->ctrl->admin_q);
> >   	put_disk(ns->disk);
> >   	nvme_put_ns_head(ns->head);
> >   	nvme_put_ctrl(ns->ctrl);
> > @@ -3903,9 +3904,14 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, struct nvme_ns_info *info)
> >   	struct gendisk *disk;
> >   	int node = ctrl->numa_node;
> >   
> 
> would be a good idea to add a comment at both places to explain why we 
> are taking this additional reference ? since this is specifically needed 
> for userspace.

Yes, it needs documentation, I believe it is because the reference of
`struct nvme_ctrl` doesn't cover ctrl->admin_queue & ctrl->admin_tagset.

Thanks,
Ming