linux-kernel - [PATCH] time: settimeofday: validate the values of tv fomr user

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Date:	Mon,  1 Dec 2014 23:04:09 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	linux-kernel@...r.kernel.org
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] time: settimeofday: validate the values of tv fomr user

An unvalidated user input is multiplied by a constant, which can result in
an undefined behaviour for large values. While this is validated later,
we should avoid triggering undefined behaviour.

Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
---
 kernel/time/time.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/time/time.c b/kernel/time/time.c
index 9ec4fa5..6f53df7 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -200,6 +200,10 @@ SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
 	if (tv) {
 		if (copy_from_user(&user_tv, tv, sizeof(*tv)))
 			return -EFAULT;
+
+		if (user_tv.tv_usec > USEC_PER_SEC || user_tv.tv_usec < 0)
+			return -EINVAL;
+
 		new_ts.tv_sec = user_tv.tv_sec;
 		new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
 	}
-- 
1.7.10.4

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