linux-kernel - [PATCH 3.16.y-ckt 004/135] time: settimeofday: Validate the values of tv from user

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Message-Id: <1423224113-10958-5-git-send-email-luis.henriques@canonical.com>
Date:	Fri,  6 Feb 2015 11:59:42 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	John Stultz <john.stultz@...aro.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 004/135] time: settimeofday: Validate the values of tv from user

3.16.7-ckt6 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sasha Levin <sasha.levin@...cle.com>

commit 6ada1fc0e1c4775de0e043e1bd3ae9d065491aa5 upstream.

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.

Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
[jstultz: include trivial milisecond->microsecond correction noticed
by Andy]
Signed-off-by: John Stultz <john.stultz@...aro.org>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 include/linux/time.h | 13 +++++++++++++
 kernel/time.c        |  4 ++++
 2 files changed, 17 insertions(+)

diff --git a/include/linux/time.h b/include/linux/time.h
index d5d229b2e5af..7d532a32ff3a 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -173,6 +173,19 @@ extern void getboottime(struct timespec *ts);
 extern void monotonic_to_bootbased(struct timespec *ts);
 extern void get_monotonic_boottime(struct timespec *ts);
 
+static inline bool timeval_valid(const struct timeval *tv)
+{
+	/* Dates before 1970 are bogus */
+	if (tv->tv_sec < 0)
+		return false;
+
+	/* Can't have more microseconds then a second */
+	if (tv->tv_usec < 0 || tv->tv_usec >= USEC_PER_SEC)
+		return false;
+
+	return true;
+}
+
 extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
 extern int timekeeping_valid_for_hres(void);
 extern u64 timekeeping_max_deferment(void);
diff --git a/kernel/time.c b/kernel/time.c
index 3c49ab45f822..3eb322e518a3 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -195,6 +195,10 @@ SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
 	if (tv) {
 		if (copy_from_user(&user_tv, tv, sizeof(*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;
 	}
-- 
2.1.4

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