On Fri, 10 Nov 2017 12:40:39 +0200, Felipe Balbi wrote:

John Keeping john@metanate.com writes:

...

This check has gone through several incompatible variations in commits 53642399aa71 ("usb: gadget: f_fs: Fix wrong check on reserved1 of OS_DESC_EXT_COMPAT"), 354bc45bf329 ("usb: gadget: f_fs: Fix ExtCompat descriptor validation") and 3ba534df815f ("Revert "usb: gadget: f_fs: Fix ExtCompat descriptor validation"") after initially being introduced in commit f0175ab51993 ("usb: gadget: f_fs: OS descriptors support").

The various changes make it impossible for a single userspace implementation to work with different kernel versions, so let's just drop the condition to avoid breaking userspace.

Fixes: 53642399aa71 ("usb: gadget: f_fs: Fix wrong check on reserved1 of OS_DESC_EXT_COMPAT") Cc: stable@vger.kernel.org # v4.7+ Signed-off-by: John Keeping john@metanate.com

---

drivers/usb/gadget/function/f_fs.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 652397eda6d6..0d9962834345 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -2282,8 +2282,7 @@ static int __ffs_data_do_os_desc(enum ffs_os_desc_type type, int i; if (len < sizeof(*d) ||

•     d->bFirstInterfaceNumber >= ffs->interfaces_count ||
  

•     !d->Reserved1)
  

•     d->bFirstInterfaceNumber >= ffs->interfaces_count)
  return -EINVAL;
  

  for (i = 0; i < ARRAY_SIZE(d->Reserved2); ++i) if (d->Reserved2[i])

Sorry, but no. We want to be compliant with the specification. If there are older still-maintained stable trees which are not working, we need to backport a fix to them, but we're not allowing uncompliant implementations.

Aren't we allowing non-compliant implementations now? The spec says the value must be 1 but since v4.7 this code has allowed all non-zero values.

At this point I don't think the kernel can disallow any values of Reserved1 without breaking someone's userspace.