Messages in this thread Patch in this message | | | From | Michal Nazarewicz <> | Subject | [PATCH 1/2] usb: f_fs: refactor and document __ffs_ep0_read_events better | Date | Wed, 10 Sep 2014 17:50:24 +0200 |
| |
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@oracle.com> Signed-off-by: Michal Nazarewicz <mina86@mina86.com> --- This has been compile tested only.
drivers/usb/gadget/function/f_fs.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index dc30adf1..ec50e0d 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -385,14 +385,16 @@ 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)]; unsigned i = 0; memset(events, 0, sizeof events); @@ -405,12 +407,10 @@ 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); @@ -2293,6 +2293,13 @@ 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 will be at most four + * pending evens on the ffs->ev.types queue. This is important since + * that array has only place for four elements and __ffs_event_add + * function also depends on that limit. 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; -- 2.1.0.rc2.206.gedb03e5
| |