Bug in 2.4.19-pre8 drivers/input/joydev.c

[Robert T. Johnson]

Sailesh Krishmurthy and I have found what we believe is an exploitable
bug in drivers/input/joydev.c:joydev_ioctl().  It looks like the
JSIOCSAXMAP and JSIOCSBTNMAP cases accidentally reverse the arguments to
copy_from_user().  A user program could call these ioctls with a
maliciously chosen arg to crash the system or gain root access.  A patch
is attached to this message (though my mailer will probably mangle it --
sorry).  We apologize if we have misunderstood the behavior of this
function.

We found this bug using the static analysis tool cqual,
http://www.cs.berkeley.edu/~jfoster/cqual/, developed at UC Berkeley by
Jeff Foster, John Kodumal, and many others.

Please CC us in any replies.

Thanks for all your great work on the kernel.

Best,
Rob Johnson ([e-mail])
Sailesh Krishnamurthy ([e-mail])

--- joydev.c    Wed May 15 10:25:26 2002
+++ joydev_fixed.c      Wed May 15 10:37:36 2002
@@ -363,7 +363,7 @@
                        return copy_to_user((struct js_corr *) arg,
joydev->corr,
                                                sizeof(struct js_corr) *
joydev->nabs) ? -EFAULT : 0;
                case JSIOCSAXMAP:
-                       if (copy_from_user((__u8 *) arg, joydev->abspam,
sizeof(__u8) *
ABS_MAX))
+                       if (copy_from_user(joydev->abspam, (__u8 *) arg,
sizeof(__u8) *
ABS_MAX))
                                return -EFAULT;
                        for (i = 0; i < ABS_MAX; i++) {
                                if (joydev->abspam[i] > ABS_MAX) return
-EINVAL;
@@ -374,7 +374,7 @@
                        return copy_to_user((__u8 *) arg,
joydev->abspam,
                                                sizeof(__u8) * ABS_MAX)
? -EFAULT : 0;
                case JSIOCSBTNMAP:
-                       if (copy_from_user((__u16 *) arg,
joydev->absmap, sizeof(__u16) *
(KEY_MAX - BTN_MISC)))
+                       if (copy_from_user(joydev->absmap, (__u16 *)
arg, sizeof(__u16) *
(KEY_MAX - BTN_MISC)))
                                return -EFAULT;
                        for (i = 0; i < KEY_MAX - BTN_MISC; i++); {
                                if (joydev->keypam[i] > KEY_MAX ||
joydev->keypam[i] < BTN_MISC)
return -EINVAL;