USB: yurex: Fix buffer over-read in yurex_write()

BugLink: https://bugs.launchpad.net/bugs/1836117
commit 7e10f14ebface44a48275c8d6dc1caae3668d5a9 upstream.

If the written data starts with a digit, yurex_write() tries to parse
it as an integer using simple_strtoull().  This requires a null-
terminator, and currently there's no guarantee that there is one.

(The sample program at
https://github.com/NeoCat/YUREX-driver-for-Linux/blob/master/sample/yurex_clock.pl
writes an integer without a null terminator.  It seems like it must
have worked by chance!)

Always add a null byte after the written data.  Enlarge the buffer
to allow for this.

Cc: stable@vger.kernel.org
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
index 3be40eaa1ac9b2caf493a8fd21e8980982b5d9a1..1232dd49556d29b00af98c347d0515c9ae91cbc7 100644 (file)
--- a/drivers/usb/misc/yurex.c
+++ b/drivers/usb/misc/yurex.c
@@ -421,13 +421,13 @@ static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
 {
        struct usb_yurex *dev;
        int i, set = 0, retval = 0;
-       char buffer[16];
+       char buffer[16 + 1];
        char *data = buffer;
        unsigned long long c, c2 = 0;
        signed long timeout = 0;
        DEFINE_WAIT(wait);
 
-       count = min(sizeof(buffer), count);
+       count = min(sizeof(buffer) - 1, count);
        dev = file->private_data;
 
        /* verify that we actually have some data to write */
@@ -446,6 +446,7 @@ static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
                retval = -EFAULT;
                goto error;
        }
+       buffer[count] = 0;
        memset(dev->cntl_buffer, CMD_PADDING, YUREX_BUF_SIZE);
 
        switch (buffer[0]) {