Messages in this thread Patch in this message | | | Date | Mon, 27 Nov 2017 18:15:40 +0000 | From | John Keeping <> | Subject | [PATCH v2] 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> --- drivers/usb/gadget/function/f_fs.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
On Mon, 27 Nov 2017 13:34:20 +0200, Felipe Balbi wrote:
> exactly like that. Care to send as a formal patch so I can apply?
Here it is.
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 97ea059a7aa4..7537cc1a7d79 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; -- 2.15.0
| |