From 11a1db99b93dbb5f7b78cffe9b85e616ab749776 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Tue, 12 Dec 2017 14:25:13 -0500 Subject: [PATCH] USB: core: prevent malicious bNumInterfaces overflow 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 Reported-by: Andrey Konovalov Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/usb/core/config.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c index 9e0c680f0922c..0a80b59917731 100644 --- a/drivers/usb/core/config.c +++ b/drivers/usb/core/config.c @@ -521,6 +521,9 @@ static int usb_parse_configuration(struct usb_device *dev, int cfgidx, 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) { @@ -534,7 +537,6 @@ static int usb_parse_configuration(struct usb_device *dev, int cfgidx, 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", -- 2.47.2