On Wed, May 11, 2022 at 02:34:28PM +0800, zhanghongtao (A) wrote:
> From: Hongtao Zhang <zhanghongtao22@xxxxxxxxxx>
>
> Switch the driver of the SPDK program that is being read and written from the uio_pci_generic driver to the NVMe driver
> (Unbind the UIO driver from the device and bind the NVMe driver to the device.) ,the system crashes and restarts.
> Bug reproduction: When the SPDK is reading or writing data, run the following command: /opt/spdk/setup.sh reset
Please properly wrap your lines at 72 columns like the editor asked you
to.
> The one with a higher probability of occurrence is as follows:
> PANIC: "BUG: unable to handle kernel NULL pointer dereference at 0000000000000008"
> [exception RIP: _raw_spin_lock_irqsave+30]
> RIP: ffffffff836a1cae RSP: ffff8bca9ecc3f20 RFLAGS: 00010046
> RAX: 0000000000000000 RBX: 0000000000000246 RCX: 0000000000000017
> RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000008
> RBP: 0000000000000000 R8: 000000afb34e50f9 R9: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: ffff8bca9ecc3f50
> R13: 0000000000000004 R14: 0000000000000004 R15: 0000000000000000
> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
> #7 [ffff8bca9ecc3f28] complete at ffffffff82f09bb8
> reason:After the driver switchover, the upper-layer program can still access the bar space of the NVMe disk controller and knock the doorbell.
> To solve this problem, a reference counting is added to prevent unbind execution before the application is closed or exited.
>
> Signed-off-by: Hongtao Zhang <zhanghongtao22@xxxxxxxxxx>
> Reviewed-by: Weifeng Su <suweifeng1@xxxxxxxxxx>
> ---
> drivers/uio/uio.c | 13 +++++++++++++
> include/linux/uio_driver.h | 1 +
> 2 files changed, 14 insertions(+)
>
> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> index 43afbb7c5ab9..cb8ed29a8648 100644
> --- a/drivers/uio/uio.c
> +++ b/drivers/uio/uio.c
> @@ -31,6 +31,7 @@ static int uio_major;
> static struct cdev *uio_cdev;
> static DEFINE_IDR(uio_idr);
> static const struct file_operations uio_fops;
> +static DECLARE_WAIT_QUEUE_HEAD(refc_wait);
>
> /* Protect idr accesses */
> static DEFINE_MUTEX(minor_lock);
> @@ -501,6 +502,7 @@ static int uio_open(struct inode *inode, struct file *filep)
> mutex_unlock(&idev->info_lock);
> if (ret)
> goto err_infoopen;
> + refcount_inc(&idev->dev_refc);
>
> return 0;
>
> @@ -536,6 +538,9 @@ static int uio_release(struct inode *inode, struct file *filep)
> ret = idev->info->release(idev->info, inode);
> mutex_unlock(&idev->info_lock);
>
> + if (refcount_dec_and_test(&idev->dev_refc))
> + wake_up(&refc_wait);
> +
> module_put(idev->owner);
> kfree(listener);
> put_device(&idev->dev);
> @@ -937,6 +942,7 @@ int __uio_register_device(struct module *owner,
>
> idev->owner = owner;
> idev->info = info;
> + refcount_set(&idev->dev_refc, 0);
> mutex_init(&idev->info_lock);
> init_waitqueue_head(&idev->wait);
> atomic_set(&idev->event, 0);
> @@ -1045,6 +1051,7 @@ void uio_unregister_device(struct uio_info *info)
> {
> struct uio_device *idev;
> unsigned long minor;
> + unsigned int dref_count;
>
> if (!info || !info->uio_dev)
> return;
> @@ -1052,6 +1059,12 @@ void uio_unregister_device(struct uio_info *info)
> idev = info->uio_dev;
> minor = idev->minor;
>
> + dref_count = refcount_read(&idev->dev_refc);
> + if (dref_count > 0) {
You can not do this, it could have changed right after reading this.
Also we went through this many times in the past already, why submit
this type of change again?
thanks,
greg k-h
