[PATCH 4.4 118/266] USB: core: Fix unterminated string returned by usb_string()
- Date: Wed, 15 May 2019 12:53:45 +0200
- From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
- Subject: [PATCH 4.4 118/266] USB: core: Fix unterminated string returned by usb_string()
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
commit c01c348ecdc66085e44912c97368809612231520 upstream.
Some drivers (such as the vub300 MMC driver) expect usb_string() to
return a properly NUL-terminated string, even when an error occurs.
(In fact, vub300's probe routine doesn't bother to check the return
code from usb_string().) When the driver goes on to use an
unterminated string, it leads to kernel errors such as
stack-out-of-bounds, as found by the syzkaller USB fuzzer.
An out-of-range string index argument is not at all unlikely, given
that some devices don't provide string descriptors and therefore list
0 as the value for their string indexes. This patch makes
usb_string() return a properly terminated empty string along with the
-EINVAL error code when an out-of-range index is encountered.
And since a USB string index is a single-byte value, indexes >= 256
are just as invalid as values of 0 or below.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
drivers/usb/core/message.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
@@ -820,9 +820,11 @@ int usb_string(struct usb_device *dev, i
if (dev->state == USB_STATE_SUSPENDED)
- if (size <= 0 || !buf || !index)
+ if (size <= 0 || !buf)
buf = 0;
+ if (index <= 0 || index >= 256)
+ return -EINVAL;
tbuf = kmalloc(256, GFP_NOIO);