linux-kernel - [PATCH 3.2 089/152] time: settimeofday: Validate the values of tv from user

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Message-ID: <lsq.1424137613.311477857@decadent.org.uk>
Date:	Tue, 17 Feb 2015 01:46:53 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Ingo Molnar" <mingo@...nel.org>,
	"John Stultz" <john.stultz@...aro.org>,
	"Sasha Levin" <sasha.levin@...cle.com>,
	"Thomas Gleixner" <tglx@...utronix.de>
Subject: [PATCH 3.2 089/152] time: settimeofday: Validate the values of tv
 from user

3.2.67-rc1 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>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 include/linux/time.h | 13 +++++++++++++
 kernel/time.c        |  4 ++++
 2 files changed, 17 insertions(+)

--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -138,6 +138,19 @@ static inline bool timespec_valid_strict
 	return true;
 }
 
+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 void read_persistent_clock(struct timespec *ts);
 extern void read_boot_clock(struct timespec *ts);
 extern int update_persistent_clock(struct timespec now);
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -192,6 +192,10 @@ SYSCALL_DEFINE2(settimeofday, struct tim
 	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;
 	}

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