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List:       git-commits-head
Subject:    USB: usb_get_string should check the descriptor type
From:       Linux Kernel Mailing List <linux-kernel () vger ! kernel ! org>
Date:       2009-02-28 2:01:50
Message-ID: 200902280201.n1S21oe9013496 () hera ! kernel ! org
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Gitweb:     http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=67f5a4ba9741fcef3f4db3509ad03565d9e33af2
Commit:     67f5a4ba9741fcef3f4db3509ad03565d9e33af2
Parent:     54b9ed35aea88b05d711884a3c2dc21bba047bd8
Author:     Alan Stern <stern@rowland.harvard.edu>
AuthorDate: Fri Feb 20 16:33:08 2009 -0500
Committer:  Greg Kroah-Hartman <gregkh@suse.de>
CommitDate: Fri Feb 27 14:40:50 2009 -0800

    USB: usb_get_string should check the descriptor type
    
    This patch (as1218) fixes a problem with a radio-control joystick used
    in the "walkera 4#3" helicopter.  This device responds to the initial
    Get-String-Descriptor request for string 0 (which is really the list
    of supported languages) by sending its config descriptor!  The
    usb_get_string() routine needs to check whether it got the right
    type of descriptor.
    
    Oddly enough, this sort of check is already present in
    usb_get_descriptor().  The patch changes the error code from -EPROTO
    to -ENODATA, because -EPROTO shows up in so many other contexts to
    indicate a hardware failure rather than a firmware error.
    
    Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
    Tested-by: Guillermo Jarabo <williamjap@gmail.com>
    Cc: stable <stable@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    
    ===================================================================
---
 drivers/usb/core/message.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 31fb204..49e7f56 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -653,7 +653,7 @@ int usb_get_descriptor(struct usb_device *dev, unsigned char type,
 		if (result <= 0 && result != -ETIMEDOUT)
 			continue;
 		if (result > 1 && ((u8 *)buf)[1] != type) {
-			result = -EPROTO;
+			result = -ENODATA;
 			continue;
 		}
 		break;
@@ -696,8 +696,13 @@ static int usb_get_string(struct usb_device *dev, unsigned short langid,
 			USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
 			(USB_DT_STRING << 8) + index, langid, buf, size,
 			USB_CTRL_GET_TIMEOUT);
-		if (!(result == 0 || result == -EPIPE))
-			break;
+		if (result == 0 || result == -EPIPE)
+			continue;
+		if (result > 1 && ((u8 *) buf)[1] != USB_DT_STRING) {
+			result = -ENODATA;
+			continue;
+		}
+		break;
 	}
 	return result;
 }
--
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