linux-kernel - [PATCH 3.4 088/176] time: settimeofday: Validate the values of tv from user

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Date:	Thu,  9 Apr 2015 16:45:36 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Sasha Levin <sasha.levin@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	John Stultz <john.stultz@...aro.org>,
	Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 088/176] time: settimeofday: Validate the values of tv from user

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

3.4.107-rc1 review patch.  If anyone has any objections, please let me know.

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


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>
[lizf: Backported to 3.4: adjust filename]
Signed-off-by: Zefan Li <lizefan@...wei.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 03dce74..bf1bb61 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -189,6 +189,19 @@ 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 a095290..0864d70 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -186,6 +186,10 @@ 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;
 	}
-- 
1.9.1

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