Patch "tty/vt/keyboard: fix OOB access in do_compute_shiftstate()" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

tty/vt/keyboard: fix OOB access in do_compute_shiftstate()

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tty-vt-keyboard-fix-oob-access-in-do_compute_shiftstate.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dmitry Torokhov <[email protected]>
Date: Mon, 27 Jun 2016 14:12:34 -0700
Subject: tty/vt/keyboard: fix OOB access in do_compute_shiftstate()

From: Dmitry Torokhov <[email protected]>

commit 510cccb5b0c8868a2b302a0ab524da7912da648b upstream.

The size of individual keymap in drivers/tty/vt/keyboard.c is NR_KEYS, which is currently 256, whereas number of keys/buttons in input device (and therefor in key_down) is much larger - KEY_CNT - 768, and that can cause out-of-bound access when we do

	sym = U(key_maps[0][k]);

with large 'k'.

To fix it we should not attempt iterating beyond smaller of NR_KEYS and KEY_CNT.

Also while at it let's switch to for_each_set_bit() instead of open-coding it.

---
 drivers/tty/vt/keyboard.c |   30 +++++++++---------------------
 1 file changed, 9 insertions(+), 21 deletions(-)

@@ -365,34 +365,22 @@ static void to_utf8(struct vc_data *vc,
 
 static void do_compute_shiftstate(void)
 {
-	unsigned int i, j, k, sym, val;
+	unsigned int k, sym, val;
 
 	shift_state = 0;
 	memset(shift_down, 0, sizeof(shift_down));
 
-	for (i = 0; i < ARRAY_SIZE(key_down); i++) {
-
-		if (!key_down[i])
+	for_each_set_bit(k, key_down, min(NR_KEYS, KEY_CNT)) {
+		sym = U(key_maps[0][k]);
+		if (KTYP(sym) != KT_SHIFT && KTYP(sym) != KT_SLOCK)
 			continue;
 
-		k = i * BITS_PER_LONG;
-
-		for (j = 0; j < BITS_PER_LONG; j++, k++) {
-
-			if (!test_bit(k, key_down))
-				continue;
-
-			sym = U(key_maps[0][k]);
-			if (KTYP(sym) != KT_SHIFT && KTYP(sym) != KT_SLOCK)
-				continue;
-
-			val = KVAL(sym);
-			if (val == KVAL(K_CAPSSHIFT))
-				val = KVAL(K_SHIFT);
+		val = KVAL(sym);
+		if (val == KVAL(K_CAPSSHIFT))
+			val = KVAL(K_SHIFT);
 
-			shift_down[val]++;
-			shift_state |= (1 << val);
-		}
+		shift_down[val]++;
+		shift_state |= BIT(val);
 	}
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/tty-vt-keyboard-fix-oob-access-in-do_compute_shiftstate.patch