Re: [PATCH v2] USB: core: Avoid WARNings for 0-length descriptor requests
From: Johan Hovold <johan@kernel.org>
Date: 2021-06-07 15:26:48
On Mon, Jun 07, 2021 at 11:23:07AM -0400, Alan Stern wrote:
The USB core has utility routines to retrieve various types of descriptors. These routines will now provoke a WARN if they are asked to retrieve 0 bytes (USB "receive" requests must not have zero length), so avert this by checking the size argument at the start. Reported-and-tested-by: syzbot+7dbcd9ff34dc4ed45240@syzkaller.appspotmail.com Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: Johan Hovold <johan@kernel.org> --- v2: Added extra blank lines following the sanity tests.
Even better. Reviewed-by: Johan Hovold <johan@kernel.org>
quoted hunk ↗ jump to hunk
drivers/usb/core/message.c | 6 ++++++ 1 file changed, 6 insertions(+) Index: usb-devel/drivers/usb/core/message.c ===================================================================--- usb-devel.orig/drivers/usb/core/message.c +++ usb-devel/drivers/usb/core/message.c@@ -783,6 +783,9 @@ int usb_get_descriptor(struct usb_device int i; int result; + if (size <= 0) /* No point in asking for no data */ + return -EINVAL; + memset(buf, 0, size); /* Make sure we parse really received data */ for (i = 0; i < 3; ++i) {@@ -832,6 +835,9 @@ static int usb_get_string(struct usb_dev int i; int result; + if (size <= 0) /* No point in asking for no data */ + return -EINVAL; + for (i = 0; i < 3; ++i) { /* retry on length 0 or stall; some devices are flakey */ result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),