4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Alan Stern stern@rowland.harvard.edu
commit 48a4ff1c7bb5a32d2e396b03132d20d552c0eca7 upstream.
A malicious USB device with crafted descriptors can cause the kernel to access unallocated memory by setting the bNumInterfaces value too high in a configuration descriptor. Although the value is adjusted during parsing, this adjustment is skipped in one of the error return paths.
This patch prevents the problem by setting bNumInterfaces to 0 initially. The existing code already sets it to the proper value after parsing is complete.
Signed-off-by: Alan Stern stern@rowland.harvard.edu Reported-by: Andrey Konovalov andreyknvl@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/usb/core/config.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/drivers/usb/core/config.c +++ b/drivers/usb/core/config.c @@ -550,6 +550,9 @@ static int usb_parse_configuration(struc unsigned iad_num = 0;
memcpy(&config->desc, buffer, USB_DT_CONFIG_SIZE); + nintf = nintf_orig = config->desc.bNumInterfaces; + config->desc.bNumInterfaces = 0; // Adjusted later + if (config->desc.bDescriptorType != USB_DT_CONFIG || config->desc.bLength < USB_DT_CONFIG_SIZE || config->desc.bLength > size) { @@ -563,7 +566,6 @@ static int usb_parse_configuration(struc buffer += config->desc.bLength; size -= config->desc.bLength;
- nintf = nintf_orig = config->desc.bNumInterfaces; if (nintf > USB_MAXINTERFACES) { dev_warn(ddev, "config %d has too many interfaces: %d, " "using maximum allowed: %d\n",