On Thu, Mar 11, 2021 at 07:27:37PM -0700, Shuah Khan wrote:
> vhci_shutdown_connection() references connection state (tcp_socket,
> tcp_rx, tcp_tx, sockfd) saved in usbpip_device without holding the
> lock.
>
> Current connection tear down sequence:
> Step 1: shutdown the socket
> Step 2: stop rx thread and reset tcp_rx pointer
> Step 3: stop tx thread and reset tcp_tx pointer
> Step 4: Reset tcp_socket and sockfd
>
> There are several race windows between these steps. In addition, device
> reset routine (vhci_device_reset) resets tcp_socket and sockfd holding
> the lock.
>
> Fix these races:
> - Introduce in_disconnect flag to ensure vhci_shutdown_connection() runs
> only once.
> - Change attach_store() to initialize in_disconnect to false while
> initializing connection status (tcp_socket, tcp_rx, tcp_tx, sockfd)
> - Change vhci_shutdown_connection() to check in_disconnect and bail
> out if disconnect is in progress.
> - Change vhci_shutdown_connection() to
> -- hold lock to save connection state pointers and unlock.
> -- Shutdown the socket and stop threads.
> -- Hold lock to clear connection status and in_disconnect flag.
> - Change vhci_device_reset() to reset tcp_socket and sockfd.
> if !in_disconnect
>
> Tested syzbot and the reproducer did not trigger any issue.
>
> Reported-and-tested-by: syzbot+a93fba6d384346a761e3@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/usb/usbip/usbip_common.h | 1 +
> drivers/usb/usbip/vhci_hcd.c | 55 +++++++++++++++++++++++---------
> drivers/usb/usbip/vhci_sysfs.c | 4 +++
> 3 files changed, 45 insertions(+), 15 deletions(-)
> diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
> index 3209b5ddd30c..c1917efe5737 100644
> --- a/drivers/usb/usbip/vhci_hcd.c
> +++ b/drivers/usb/usbip/vhci_hcd.c
> @@ -1007,31 +1007,54 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
> static void vhci_shutdown_connection(struct usbip_device *ud)
> {
> struct vhci_device *vdev = container_of(ud, struct vhci_device, ud);
> + unsigned long flags;
> + struct socket *socket;
> + struct task_struct *tcp_rx = NULL;
> + struct task_struct *tcp_tx = NULL;
> + int sockfd = 0;
> +
> + spin_lock_irqsave(&ud->lock, flags);
> + if (vdev->ud.in_disconnect) {
> + pr_info("%s: Disconnect in progress for sockfd %d\n",
> + __func__, ud->sockfd);
Looks like you forgot to remove all you debug printks like this one
before submitting.
> + spin_unlock_irqrestore(&ud->lock, flags);
> + return;
> + }
Johan
