Instead of using variable length array, use a static length equal to
the size of the ffs->ev.types array. This gets rid of a sparse warning:
drivers/usb/gadget/function/f_fs.c:401:44: warning:
Variable length array is used.
and makes it more explicit that the array has a very tight upper size
limit. Also add some more documentation about the ev.types array and
how its size is limited and affects the rest of the code.
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reported-by: Rohith Seelaboyina <rseelaboyina@xxxxxxxxxx>
Signed-off-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
---
drivers/usb/gadget/function/f_fs.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 63314ed..a00ee97 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -390,17 +390,20 @@ done_spin:
return ret;
}
+/* Called with ffs->ev.waitq.lock and ffs->mutex held, both released on exit. */
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.
+ * n cannot be bigger than ffs->ev.count, which cannot be bigger than
+ * size of ffs->ev.types array (which is four) so that's how much space
+ * we reserve.
*/
- struct usb_functionfs_event events[n];
+ struct usb_functionfs_event events[ARRAY_SIZE(ffs->ev.types)];
+ const size_t size = n * sizeof *events;
unsigned i = 0;
- memset(events, 0, sizeof events);
+ memset(events, 0, size);
do {
events[i].type = ffs->ev.types[i];
@@ -410,19 +413,15 @@ static ssize_t __ffs_ep0_read_events(struct ffs_data *ffs, char __user *buf,
}
} while (++i < n);
- if (n < ffs->ev.count) {
- ffs->ev.count -= n;
+ ffs->ev.count -= n;
+ if (ffs->ev.count)
memmove(ffs->ev.types, ffs->ev.types + n,
ffs->ev.count * sizeof *ffs->ev.types);
- } else {
- ffs->ev.count = 0;
- }
spin_unlock_irq(&ffs->ev.waitq.lock);
mutex_unlock(&ffs->mutex);
- return unlikely(__copy_to_user(buf, events, sizeof events))
- ? -EFAULT : sizeof events;
+ return unlikely(__copy_to_user(buf, events, size)) ? -EFAULT : size;
}
static ssize_t ffs_ep0_read(struct file *file, char __user *buf,
@@ -2377,6 +2376,13 @@ static void __ffs_event_add(struct ffs_data *ffs,
if (ffs->setup_state == FFS_SETUP_PENDING)
ffs->setup_state = FFS_SETUP_CANCELLED;
+ /*
+ * Logic of this function guarantees that there are at most four pending
+ * evens on ffs->ev.types queue. This is important because the queue
+ * has space for four elements only and __ffs_ep0_read_events function
+ * depends on that limit as well. If more event types are added, those
+ * limits have to be revisited or guaranteed to still hold.
+ */
switch (type) {
case FUNCTIONFS_RESUME:
rem_type2 = FUNCTIONFS_SUSPEND;
--
2.2.0.rc0.207.ga3a616c
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