On Thu, 11 Oct 2012, Henrik Rydberg wrote:
> From 40b70394747eea51fdd07cc8213dd6afd24b1b30 Mon Sep 17 00:00:00 2001
> From: Henrik Rydberg <rydb...@euromail.se>
> Date: Thu, 11 Oct 2012 23:27:04 +0200
> Subject: [PATCH] usbdevfs: Fix broken scatter-gather transfer
>
> The recently introduced handling of large bulk transfers is completely
> broken; the same user page is read over and over again. Fixed with
> this patch.
>
> Cc: sta...@kernel.org
> Signed-off-by: Henrik Rydberg <rydb...@euromail.se>
> ---
> drivers/usb/core/devio.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
> index ebb8a9d..6e58b59 100644
> --- a/drivers/usb/core/devio.c
> +++ b/drivers/usb/core/devio.c
> @@ -1172,6 +1172,7 @@ static int proc_do_submiturb(struct dev_state *ps,
> struct usbdevfs_urb *uurb,
> struct usb_ctrlrequest *dr = NULL;
> unsigned int u, totlen, isofrmlen;
> int i, ret, is_in, num_sgs = 0, ifnum = -1;
> + void __user *userbuf;
> void *buf;
>
> if (uurb->flags & ~(USBDEVFS_URB_ISO_ASAP |
> @@ -1333,6 +1334,7 @@ static int proc_do_submiturb(struct dev_state *ps,
> struct usbdevfs_urb *uurb,
> as->urb->num_sgs = num_sgs;
> sg_init_table(as->urb->sg, as->urb->num_sgs);
>
> + userbuf = uurb->buffer;
> totlen = uurb->buffer_length;
> for (i = 0; i < as->urb->num_sgs; i++) {
> u = (totlen > USB_SG_SIZE) ? USB_SG_SIZE : totlen;
> @@ -1344,11 +1346,12 @@ static int proc_do_submiturb(struct dev_state *ps,
> struct usbdevfs_urb *uurb,
> sg_set_buf(&as->urb->sg[i], buf, u);
>
> if (!is_in) {
> - if (copy_from_user(buf, uurb->buffer, u)) {
> + if (copy_from_user(buf, userbuf, u)) {
> ret = -EFAULT;
> goto error;
> }
> }
> + userbuf += u;
Instead of introducing a new local variable, why not simply update
uurb->buffer? That's what we do elsewhere in the code.
Alan Stern
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