On Mon, 12 Dec 2016, Mateusz Berezecki wrote:
> Promote a variable keeping track of USB transfer memory usage to a
> wider data type and allow for higher bandwidth transfers from a large
> number of USB devices connected to a single host.
> ---
> drivers/usb/core/devio.c | 34 ++++++++++++----------------------
> 1 file changed, 12 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
> index 4016dae..bead975 100644
> --- a/drivers/usb/core/devio.c
> +++ b/drivers/usb/core/devio.c
> @@ -134,42 +134,32 @@ enum snoop_when {
> #define USB_DEVICE_DEV MKDEV(USB_DEVICE_MAJOR, 0)
>
> /* Limit on the total amount of memory we can allocate for transfers */
> -static unsigned usbfs_memory_mb = 16;
> +static u32 usbfs_memory_mb = 16;
> module_param(usbfs_memory_mb, uint, 0644);
> MODULE_PARM_DESC(usbfs_memory_mb,
> "maximum MB allowed for usbfs buffers (0 = no limit)");
>
> -/* Hard limit, necessary to avoid arithmetic overflow */
> -#define USBFS_XFER_MAX (UINT_MAX / 2 - 1000000)
> -
> -static atomic_t usbfs_memory_usage; /* Total memory currently allocated */
> +static atomic64_t usbfs_memory_usage; /* Total memory currently allocated */
>
> /* Check whether it's okay to allocate more memory for a transfer */
> -static int usbfs_increase_memory_usage(unsigned amount)
> +static int usbfs_increase_memory_usage(u64 amount)
> {
> - unsigned lim;
> + u64 lim;
>
> - /*
> - * Convert usbfs_memory_mb to bytes, avoiding overflows.
> - * 0 means use the hard limit (effectively unlimited).
> - */
> lim = ACCESS_ONCE(usbfs_memory_mb);
> - if (lim == 0 || lim > (USBFS_XFER_MAX >> 20))
> - lim = USBFS_XFER_MAX;
> - else
> - lim <<= 20;
> + lim <<= 20;
You need to handle the case where lim == 0 (see the MODULE_PARM_DESC
text).
>
> - atomic_add(amount, &usbfs_memory_usage);
> - if (atomic_read(&usbfs_memory_usage) <= lim)
> + atomic64_add(amount, &usbfs_memory_usage);
> + if (atomic64_read(&usbfs_memory_usage) <= lim)
> return 0;
> - atomic_sub(amount, &usbfs_memory_usage);
> + atomic64_sub(amount, &usbfs_memory_usage);
> return -ENOMEM;
> }
>
> /* Memory for a transfer is being deallocated */
> -static void usbfs_decrease_memory_usage(unsigned amount)
> +static void usbfs_decrease_memory_usage(u64 amount)
> {
> - atomic_sub(amount, &usbfs_memory_usage);
> + atomic64_sub(amount, &usbfs_memory_usage);
> }
>
> static int connected(struct usb_dev_state *ps)
> @@ -1191,7 +1181,7 @@ static int proc_bulk(struct usb_dev_state *ps, void __user *arg)
> if (!usb_maxpacket(dev, pipe, !(bulk.ep & USB_DIR_IN)))
> return -EINVAL;
> len1 = bulk.len;
> - if (len1 >= USBFS_XFER_MAX)
> + if (len1 >= (INT_MAX - sizeof(struct urb)))
> return -EINVAL;
> ret = usbfs_increase_memory_usage(len1 + sizeof(struct urb));
> if (ret)
> @@ -1584,7 +1574,7 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb
> return -EINVAL;
> }
>
> - if (uurb->buffer_length >= USBFS_XFER_MAX) {
> + if (uurb->buffer_length >= (INT_MAX - sizeof(struct urb))) {
> ret = -EINVAL;
> goto error;
> }
This isn't right. See how the u variable gets used in this routine.
You have to guarantee that the computation of u won't overflow.
Alan Stern
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