vt: keyboard: avoid signed integer overflow in k_ascii
commit b86dab054059b970111b5516ae548efaae5b3aae upstream.
When k_ascii is invoked several times in a row there is a potential for
signed integer overflow:
UBSAN: Undefined behaviour in drivers/tty/vt/keyboard.c:888:19 signed integer overflow:
10 * 1111111111 cannot be represented in type 'int'
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.11 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0xce/0x128 lib/dump_stack.c:118
ubsan_epilogue+0xe/0x30 lib/ubsan.c:154
handle_overflow+0xdc/0xf0 lib/ubsan.c:184
__ubsan_handle_mul_overflow+0x2a/0x40 lib/ubsan.c:205
k_ascii+0xbf/0xd0 drivers/tty/vt/keyboard.c:888
kbd_keycode drivers/tty/vt/keyboard.c:1477 [inline]
kbd_event+0x888/0x3be0 drivers/tty/vt/keyboard.c:1495
While it can be worked around by using check_mul_overflow()/
check_add_overflow(), it is better to introduce a separate flag to
signal that number pad is being used to compose a symbol, and
change type of the accumulator from signed to unsigned, thus
avoiding undefined behavior when it overflows.
Reported-by: Kyungtae Kim <kt0755@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200525232740.GA262061@dtor-ws
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 file changed