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authorDmitry Torokhov <dmitry.torokhov@gmail.com>2020-05-25 16:27:40 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-05-27 12:21:44 +0200
commitb86dab054059b970111b5516ae548efaae5b3aae (patch)
treee5dfa264b9646af7231f50674c4f2f58a951e27f /drivers/tty/vt/keyboard.c
parent15a3f03d5ec0118f1e5db3fc1018686e72744e37 (diff)
vt: keyboard: avoid signed integer overflow in k_ascii
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/keyboard.c')
-rw-r--r--drivers/tty/vt/keyboard.c26
1 files changed, 16 insertions, 10 deletions
diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
index 15d33fa0c925..568b2171f335 100644
--- a/drivers/tty/vt/keyboard.c
+++ b/drivers/tty/vt/keyboard.c
@@ -127,7 +127,11 @@ 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 */
@@ -845,12 +849,12 @@ 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;
}
}
@@ -868,7 +872,7 @@ 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;
@@ -882,10 +886,12 @@ 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)