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authorJohn Keeping <john@metanate.com>2017-11-27 21:15:40 +0300
committerFelipe Balbi <felipe.balbi@linux.intel.com>2017-11-28 14:05:31 +0300
commita3acc696085e112733d191a77b106e67a4fa110b (patch)
tree149aa791fe110d309dfcba8db474c2b74e0ed3ca /drivers/usb
parenta4f0927ef588cf62bb864707261482c874352942 (diff)
downloadlinux-a3acc696085e112733d191a77b106e67a4fa110b.tar.xz
usb: f_fs: Force Reserved1=1 in OS_DESC_EXT_COMPAT
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 53642399aa71 ("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: 53642399aa71 ("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>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/gadget/function/f_fs.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 9aa457b53e01..b6cf5ab5a0a1 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -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;