linux-kernel - Re: [PATCH] nvme: prevent double free in nvme_alloc

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Date:   Mon, 27 Apr 2020 20:03:11 +0200
From:   Javier González <javier@...igon.com>
To:     Niklas Cassel <niklas.cassel@....com>
Cc:     Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Igor Konopko <igor.j.konopko@...el.com>,
        Matias Bjørling <mb@...htnvm.io>,
        Jens Axboe <axboe@...nel.dk>, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvme: prevent double free in nvme_alloc_ns() error
 handling

On 27.04.2020 14:34, Niklas Cassel wrote:
>When jumping to the out_put_disk label, we will call put_disk(), which will
>trigger a call to disk_release(), which calls blk_put_queue().
>
>Later in the cleanup code, we do blk_cleanup_queue(), which will also call
>blk_put_queue().
>
>Putting the queue twice is incorrect, and will generate a KASAN splat.
>
>Set the disk->queue pointer to NULL, before calling put_disk(), so that the
>first call to blk_put_queue() will not free the queue.
>
>The second call to blk_put_queue() uses another pointer to the same queue,
>so this call will still free the queue.
>
>Fixes: 85136c010285 ("lightnvm: simplify geometry enumeration")
>Signed-off-by: Niklas Cassel <niklas.cassel@....com>
>---
> drivers/nvme/host/core.c | 2 ++
> 1 file changed, 2 insertions(+)
>
>diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>index 91c1bd659947..f2adea96b04c 100644
>--- a/drivers/nvme/host/core.c
>+++ b/drivers/nvme/host/core.c
>@@ -3642,6 +3642,8 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
>
> 	return;
>  out_put_disk:
>+	/* prevent double queue cleanup */
>+	ns->disk->queue = NULL;
> 	put_disk(ns->disk);
>  out_unlink_ns:
> 	mutex_lock(&ctrl->subsys->lock);
>-- 
>2.25.3
>
What about delaying the assignment of ns->disk?

diff --git i/drivers/nvme/host/core.c w/drivers/nvme/host/core.c
index a4d8c90ee7cc..6da4a9ced945 100644
--- i/drivers/nvme/host/core.c
+++ w/drivers/nvme/host/core.c
@@ -3541,7 +3541,6 @@ static int nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
         disk->queue = ns->queue;
         disk->flags = flags;
         memcpy(disk->disk_name, disk_name, DISK_NAME_LEN);
-       ns->disk = disk;

         __nvme_revalidate_disk(disk, id);

@@ -3553,6 +3552,8 @@ static int nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
                 }
         }

+       ns->disk = disk;
+
         down_write(&ctrl->namespaces_rwsem);
         list_add_tail(&ns->list, &ctrl->namespaces);
         up_write(&ctrl->namespaces_rwsem);


Javier