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usb: f_fs: Force Reserved1=1 in OS_DESC_EXT_COMPAT

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The specification says that the Reserved1 field in OS_DESC_EXT_COMPAT
must have the value "1", but when this feature was first implemented we
rejected any non-zero values.

This was adjusted to accept all non-zero values (while now rejecting
zero) in commit 53642399aa ("usb: gadget: f_fs: Fix wrong check on
reserved1 of OS_DESC_EXT_COMPAT"), but that breaks any userspace
programs that worked previously by returning EINVAL when Reserved1 == 0
which was previously the only value that succeeded!

If we just set the field to "1" ourselves, both old and new userspace
programs continue to work correctly and, as a bonus, old programs are
now compliant with the specification without having to fix anything
themselves.

Fixes: 53642399aa ("usb: gadget: f_fs: Fix wrong check on reserved1 of OS_DESC_EXT_COMPAT")
Cc: <stable@vger.kernel.org>
Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
This commit is contained in:
John Keeping 2017-11-27 18:15:40 +00:00 committed by Felipe Balbi
parent a4f0927ef5
commit a3acc69608
1 changed files with 11 additions and 2 deletions
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13
drivers/usb/gadget/function/f_fs.c
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@ -2282,9 +2282,18 @@ 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;
if (d->Reserved1 != 1) {
/*
* According to the spec, Reserved1 must be set to 1
* but older kernels incorrectly rejected non-zero
* values. We fix it here to avoid returning EINVAL
* in response to values we used to accept.
*/
pr_debug("usb_ext_compat_desc::Reserved1 forced to 1\n");
d->Reserved1 = 1;
}
for (i = 0; i < ARRAY_SIZE(d->Reserved2); ++i)
if (d->Reserved2[i])
return -EINVAL;