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@xxxxxxxxxxxxxxxxxxx>
Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
CC: <stable@xxxxxxxxxxxxxxx>
---
[as1855]
drivers/usb/core/config.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
Index: usb-4.x/drivers/usb/core/config.c
===================================================================
--- usb-4.x.orig/drivers/usb/core/config.c
+++ usb-4.x/drivers/usb/core/config.c
@@ -555,6 +555,9 @@ 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) {
@@ -568,7 +571,6 @@ 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",
--
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