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Issue of the Implementation # L0006

Brief

drivers/media/video/usbvideo/quickcam_messenger.c: Possible buffer overflow while use strncat with wrong 3rd parameter.

Detailed Description

In driver ./drivers/media/video/usbvideo/quickcam_messenger.c in line 91:

  91         usb_make_path(dev, cam->input_physname, sizeof(cam-
>input_physname));

After this line we used strncat:

  92         strncat(cam->input_physname, "/input0", sizeof(cam-
>input_physname));

where sizeof(cam->input_physname) returned length of cam->input_phisname without length for nul-symbol. But this parameter must be - "maximum numbers of bytes to copy", i.e.: sizeof(cam->input_physname)-strlen(cam- >input_physname)-1. In this case, after calls usb_make_path in similar drivers uses strlcat, like as: (example from drivers/hid/usbhid/hid-core.c):

1152         usb_make_path(dev, hid->phys, sizeof(hid->phys));
1153         strlcat(hid->phys, "/input", sizeof(hid->phys));

Possible solutions

diff --git a/./a/drivers/media/video/usbvideo/quickcam_messenger.c 
b/./b/drivers/media/video/usbvideo/quickcam_messenger.c
index 803d3e4..c4d1b96 100644
--- a/./a/drivers/media/video/usbvideo/quickcam_messenger.c
+++ b/./b/drivers/media/video/usbvideo/quickcam_messenger.c
@@ -89,7 +89,7 @@ static void qcm_register_input(struct qcm *cam, struct 
usb_device *dev)
 	int error;
 
 	usb_make_path(dev, cam->input_physname, sizeof(cam->input_physname));
-	strncat(cam->input_physname, "/input0", sizeof(cam->input_physname));
+	strlcat(cam->input_physname, "/input0", sizeof(cam->input_physname));
 
 	cam->input = input_dev = input_allocate_device();
 	if (!input_dev) {

Component

linux-kernel 2.6.31

Accepted

http://lkml.org/lkml/2009/10/7/217
commit

Status

Fixed in kernel 2.6.33-rc1

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