[PATCH 3.13.y-ckt 064/103] time: settimeofday: Validate the values of tv from user

Kamal Mostafa
2015-02-19T00:47:18Z

From: Sasha Levin <sasha.levin@oracle.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@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
[jstultz: include trivial milisecond->microsecond correction noticed
by Andy]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.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 d5d229b..1949cd3 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -115,6 +115,19 @@ static inline bool timespec_valid_strict(const struct timespec *ts)
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 bool persistent_clock_exist;

static inline bool has_persistent_clock(void)
diff --git a/kernel/time.c b/kernel/time.c
index 3c49ab4..3eb322e 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;
}
--
1.9.1