From c8f26979bdb5cc5e8ad515cd750ec6e23c2a69a4 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Wed, 18 Oct 2017 12:49:38 -0400 Subject: [PATCH] USB: core: fix out-of-bounds access bug in usb_get_bos_descriptor() commit 1c0edc3633b56000e18d82fc241e3995ca18a69e upstream. Andrey used the syzkaller fuzzer to find an out-of-bounds memory access in usb_get_bos_descriptor(). The code wasn't checking that the next usb_dev_cap_header structure could fit into the remaining buffer space. This patch fixes the error and also reduces the bNumDeviceCaps field in the header to match the actual number of capabilities found, in cases where there are fewer than expected. Reported-by: Andrey Konovalov Signed-off-by: Alan Stern Tested-by: Andrey Konovalov Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/config.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c index 7008ba6a7be3f1..1bdf8bd0eb1b84 100644 --- a/drivers/usb/core/config.c +++ b/drivers/usb/core/config.c @@ -920,10 +920,12 @@ int usb_get_bos_descriptor(struct usb_device *dev) for (i = 0; i < num; i++) { buffer += length; cap = (struct usb_dev_cap_header *)buffer; - length = cap->bLength; - if (total_len < length) + if (total_len < sizeof(*cap) || total_len < cap->bLength) { + dev->bos->desc->bNumDeviceCaps = i; break; + } + length = cap->bLength; total_len -= length; if (cap->bDescriptorType != USB_DT_DEVICE_CAPABILITY) {