tty/vt/keyboard: fix OOB access in do_compute_shiftstate() (510cccb5) · Commits · 戴 / test

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. Reported-by:

Sasha Levin <sasha.levin@oracle.com> Reviewed-by:

Guenter Roeck <linux@roeck-us.net> Cc: stable@vger.kernel.org Signed-off-by:

Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/tty/vt/keyboard.c

+9 −21

Original line number	Diff line number	Diff line
		@@ -366,23 +366,12 @@ static void to_utf8(struct vc_data *vc, uint c)

		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])
		continue;

		k = i * BITS_PER_LONG;

		for (j = 0; j < BITS_PER_LONG; j++, k++) {

		if (!test_bit(k, key_down))
		continue;

		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;
		@@ -392,8 +381,7 @@ static void do_compute_shiftstate(void)
		val = KVAL(K_SHIFT);

		shift_down[val]++;
		shift_state \|= (1 << val);
		}
		shift_state \|= BIT(val);
		}
		}

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