time: settimeofday: Validate the values of tv from 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.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: stable <stable@vger.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>

2 files changed, 17 insertions, 0 deletions

diff --git a/include/linux/time.h b/include/linux/time.h
index 8c42cf8d2444..5989b0ead1ec 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -99,6 +99,19 @@ 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 struct timespec timespec_trunc(struct timespec t, unsigned gran);
 
 #define CURRENT_TIME            (current_kernel_time())
diff --git a/kernel/time/time.c b/kernel/time/time.c
index a9ae20fb0b11..22d5d3b73970 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -196,6 +196,10 @@ 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;
         }