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| author | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2020-05-25 16:27:40 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-06-11 09:21:40 +0200 |
| commit | dad0bf9ce93fa40b667eccd3306783f4db4b932b (patch) | |
| tree | d1ac6007b7b9b8f2f2ed35b01419683a0002c0b6 /drivers/tty/vt | |
| parent | 043ff85abd394d2a5806a1ba58b720ddb84d605d (diff) | |
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>
Diffstat (limited to 'drivers/tty/vt')
| -rw-r--r-- | drivers/tty/vt/keyboard.c | 26 |
1 files changed, 16 insertions, 10 deletions
diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c index fb43f8dc9246..96c65fe64141 100644 --- a/drivers/tty/vt/keyboard.c +++ b/drivers/tty/vt/keyboard.c @@ -125,7 +125,11 @@ static DEFINE_SPINLOCK(func_buf_lock); /* guard 'func_buf' and friends */ static unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; /* keyboard key bitmap */ static unsigned char shift_down[NR_SHIFT]; /* shift state counters.. */ static bool dead_key_next; -static int npadch = -1; /* -1 or number assembled on pad */ + +/* Handles a number being assembled on the number pad */ +static bool npadch_active; +static unsigned int npadch_value; + static unsigned int diacr; static char rep; /* flag telling character repeat */ @@ -815,12 +819,12 @@ static void k_shift(struct vc_data *vc, unsigned char value, char up_flag) shift_state &= ~(1 << value); /* kludge */ - if (up_flag && shift_state != old_state && npadch != -1) { + if (up_flag && shift_state != old_state && npadch_active) { if (kbd->kbdmode == VC_UNICODE) - to_utf8(vc, npadch); + to_utf8(vc, npadch_value); else - put_queue(vc, npadch & 0xff); - npadch = -1; + put_queue(vc, npadch_value & 0xff); + npadch_active = false; } } @@ -838,7 +842,7 @@ static void k_meta(struct vc_data *vc, unsigned char value, char up_flag) static void k_ascii(struct vc_data *vc, unsigned char value, char up_flag) { - int base; + unsigned int base; if (up_flag) return; @@ -852,10 +856,12 @@ static void k_ascii(struct vc_data *vc, unsigned char value, char up_flag) base = 16; } - if (npadch == -1) - npadch = value; - else - npadch = npadch * base + value; + if (!npadch_active) { + npadch_value = 0; + npadch_active = true; + } + + npadch_value = npadch_value * base + value; } static void k_lock(struct vc_data *vc, unsigned char value, char up_flag) |