On Mon, Feb 2, 2026 at 11:13 AM Zhang Tianci
<[email protected]> wrote:
>
> There is one race case in vduse_dev_msg_sync and vduse_dev_read_iter:
>
> vduse_dev_read_iter():
> lock(msg_lock);
> dequeue_msg(send_list);
> unlock(msg_lock);
> vduse_dev_msg_sync():
> wait_timeout() finish
> lock(msg_lock);
> check msg->complete is false
> list_del(msg); <- double list_del() crash!
>
> To fix this case, we shall ensure vduse_msg is on send_list or recv_list
> outside the msg_lock critical section.
>
> Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
> Cc: [email protected]
> Signed-off-by: Zhang Tianci <[email protected]>
> Reviewed-by: Xie Yongji <[email protected]>
> ---
> v2:
> - Rewrite commit message. [Michael]
> - Add Fixes tag and cc stable email list. [Eugenio]
> - Rewrite one comment. [Michael]
>
> v1: https://lkml.org/lkml/2026/1/30/323
>
> drivers/vdpa/vdpa_user/vduse_dev.c | 30 ++++++++++++++++++++++--------
> 1 file changed, 22 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c
> b/drivers/vdpa/vdpa_user/vduse_dev.c
> index ae357d014564c..a70d0580d54e8 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -325,6 +325,7 @@ static ssize_t vduse_dev_read_iter(struct kiocb *iocb,
> struct iov_iter *to)
> struct file *file = iocb->ki_filp;
> struct vduse_dev *dev = file->private_data;
> struct vduse_dev_msg *msg;
> + struct vduse_dev_request req;
> int size = sizeof(struct vduse_dev_request);
> ssize_t ret;
>
> @@ -339,7 +340,7 @@ static ssize_t vduse_dev_read_iter(struct kiocb *iocb,
> struct iov_iter *to)
>
> ret = -EAGAIN;
> if (file->f_flags & O_NONBLOCK)
> - goto unlock;
> + break;
>
> spin_unlock(&dev->msg_lock);
> ret = wait_event_interruptible_exclusive(dev->waitq,
> @@ -349,17 +350,30 @@ static ssize_t vduse_dev_read_iter(struct kiocb *iocb,
> struct iov_iter *to)
>
> spin_lock(&dev->msg_lock);
> }
> + if (!msg) {
> + spin_unlock(&dev->msg_lock);
> + return ret;
> + }
Nit: this check seems to be redundant, I'd suggest to
1) move the spin_unlock() before the check of file->f_flags & O_NONBLOCK
2) then we can simply do "return ret" when it's a nonblocking read.
> +
> + memcpy(&req, &msg->req, sizeof(req));
> + /*
> + * We must ensure vduse_msg is on send_list or recv_list before unlock
> + * dev->msg_lock. Because vduse_dev_msg_sync() may be timeout when we
> + * copy data to userspace, and will call list_del() for this msg.
> + */
> + vduse_enqueue_msg(&dev->recv_list, msg);
> spin_unlock(&dev->msg_lock);
> - ret = copy_to_iter(&msg->req, size, to);
> - spin_lock(&dev->msg_lock);
> +
> + ret = copy_to_iter(&req, size, to);
> if (ret != size) {
> + spin_lock(&dev->msg_lock);
> + /* Roll back: move msg back to send_list if still pending. */
> + msg = vduse_find_msg(&dev->recv_list, req.request_id);
> + if (msg)
> + vduse_enqueue_msg(&dev->send_list, msg);
> + spin_unlock(&dev->msg_lock);
> ret = -EFAULT;
> - vduse_enqueue_msg(&dev->send_list, msg);
> - goto unlock;
> }
> - vduse_enqueue_msg(&dev->recv_list, msg);
> -unlock:
> - spin_unlock(&dev->msg_lock);
>
> return ret;
> }
> --
> 2.39.5
>
Thanks
