[tip:timers/core] time: Validate user input in compat_settimeofday()

[tip-bot for zhengbin <tipbot@zytor.com>]

Commit-ID:  9176ab1b848059a0cd9caf39f0cebaa1b7ec5ec2
Gitweb:     https://git.kernel.org/tip/9176ab1b848059a0cd9caf39f0cebaa1b7ec5ec2
Author:     zhengbin <zhengbin13@huawei.com>
AuthorDate: Sun, 7 Jul 2019 08:51:41 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 7 Jul 2019 12:05:40 +0200

time: Validate user input in compat_settimeofday()

The user value is validated after converting the timeval to a timespec, but
for a wide range of negative tv_usec values the multiplication overflow turns
them in positive numbers. So the 'validated later' is not catching the
invalid input.

Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1562460701-113301-1-git-send-email-zhengbin13@huawei.com

---
 kernel/time/time.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/time/time.c b/kernel/time/time.c
index 7f7d6914ddd5..5c54ca632d08 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -251,6 +251,10 @@ COMPAT_SYSCALL_DEFINE2(settimeofday, struct old_timeval32 __user *, tv,
 	if (tv) {
 		if (compat_get_timeval(&user_tv, tv))
 			return -EFAULT;
+
+		if (!timeval_valid(&user_tv))
+			return -EINVAL;
+
 		new_ts.tv_sec = user_tv.tv_sec;
 		new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
 	}