usb: chipidea: debug: avoid out of bound read

commit bd5fb0aec3dd7cde7ec4c397b10e55d4c9626d8d upstream.

A string written by the user may not be zero terminated.

sscanf may read memory beyond the buffer if no zero byte
is found.

For testing build with CONFIG_USB_CHIPIDEA=y, CONFIG_USB_CHIPIDEA_DEBUG=y.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/drivers/usb/chipidea/debug.c b/drivers/usb/chipidea/debug.c
index 96d899aee473b943880972aac399178210bf1c1d..92f0cc442d4694c4a63cdbd474991f8e99b55367 100644 (file)
--- a/drivers/usb/chipidea/debug.c
+++ b/drivers/usb/chipidea/debug.c
@@ -84,9 +84,13 @@ static ssize_t ci_port_test_write(struct file *file, const char __user *ubuf,
        char buf[32];
        int ret;
 
-       if (copy_from_user(buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
+       count = min_t(size_t, sizeof(buf) - 1, count);
+       if (copy_from_user(buf, ubuf, count))
                return -EFAULT;
 
+       /* sscanf requires a zero terminated string */
+       buf[count] = '\0';
+
        if (sscanf(buf, "%u", &mode) != 1)
                return -EINVAL;