[PATCH] tty: an overflow of multiplication in drivers/tty/cyclades.c

[Qixue Xiao]

there is an overflow in the code :
cyz_polling_cycle = (arg * HZ) / 1000,
the multiplicator arg comes from user, so it may be an overflow if
arg is a big number. And the value of cyc_polling_cycle will be
wrong when it is used next time.

Reported-by: Qixue Xiao <xiaoqixue_1@xxxxxxx>
Suggested-by: Yongjian Xu <xuyongjiande@xxxxxxxxx>
Suggested-by: Yu Chen <chyyuu@xxxxxxxxx>
Signed-off-by: Qixue Xiao <xiaoqixue_1@xxxxxxx>
---
 drivers/tty/cyclades.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/tty/cyclades.c b/drivers/tty/cyclades.c
index 33f83fe..a57bb5a 100644
--- a/drivers/tty/cyclades.c
+++ b/drivers/tty/cyclades.c
@@ -2709,6 +2709,8 @@ cy_ioctl(struct tty_struct *tty,
 		break;
 #ifndef CONFIG_CYZ_INTR
 	case CYZSETPOLLCYCLE:
+		if (arg > LONG_MAX / HZ)
+			return -ENODEV;
 		cyz_polling_cycle = (arg * HZ) / 1000;
 		break;
 	case CYZGETPOLLCYCLE:
-- 
1.7.9.5

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