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From: Michał Nazarewicz on 7 Apr 2010 13:20
On Wed, 07 Apr 2010 15:41:30 +0200, Michal Nazarewicz <m.nazarewicz(a)samsung.com> wrote:
> +static ssize_t __ffs_ep0_read_events(struct ffs_data *ffs, char __user *buf,
> + size_t n)
> +{
> + /* We are holding ffs->ev.waitq.lock and ffs->mutex and we need
> + * to release them. */
> +
> + struct usb_functionfs_event events[n];
> + unsigned i = 0;
> +
> + memset(events, 0, sizeof events);
> +
> + do {
> + events[i].type = ffs->ev.types[i];
> + if (events[i].type == FUNCTIONFS_SETUP) {
> + events[i].u.setup = ffs->ev.setup;
> + ffs->setup_state = FFS_SETUP_PENDING;
> + }
> + } while (++i < n);
> +
> + ffs->ev.count = 0;

I've just noticed. This line should instead read:

+ if (n < ffs->ev.count) {
+ ffs->ev.count -= n;
+ memmove(ffs->ev.types, ffs->ev.types + n,
+ ffs->ev.count * sizeof *ffs->ev.types);
+ } else {
+ ffs->ev.count = 0;
+ }

This is a minor bug which should be rather hard to observe (and only
if user-space reads() less then 4 * sizeof(struct usb_functionfs_event)
bytes when reading from "ep0") so posted code is good for testing.
(I'll post a fixed version later on with possibly other fixes and
changes.)

> +
> + spin_unlock_irq(&ffs->ev.waitq.lock);
> + mutex_unlock(&ffs->mutex);
> +
> + return unlikely(__copy_to_user(buf, events, sizeof events))
> + ? -EFAULT : sizeof events;
> +}

--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał "mina86" Nazarewicz (o o)
ooo +---[mina86(a)mina86.com]---[mina86(a)jabber.org]---ooO--(_)--Ooo--
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Prev: linux-next: Tree for April 7 (other build fixes)
Next: [PATCH] RCU: Better explain the condition parameter of rcu_dereference_check()