linux-kernel - [PATCH] time: Validate the usec before covert to nsec in do

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Date:   Mon, 8 Jul 2019 15:55:04 +0800
From:   ZhangXiaoxu <zhangxiaoxu5@...wei.com>
To:     <john.stultz@...aro.org>, <tglx@...utronix.de>, <sboyd@...nel.org>,
        <zhangxiaoxu5@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] time: Validate the usec before covert to nsec in do_adjtimex

When covert the usec to nsec, it will multiple 1000, it maybe
overflow and lead an undefined behavior.

For example, users may input an negative tv_usec values when
call adjtimex syscall, then multiple 1000 maybe overflow it
to a positive and legal number.

So, we should validate the usec before coverted it to nsec.

Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@...wei.com>
---
 kernel/time/timekeeping.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 44b726b..e5c1d00 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1272,9 +1272,6 @@ static int timekeeping_inject_offset(const struct timespec64 *ts)
 	struct timespec64 tmp;
 	int ret = 0;
 
-	if (ts->tv_nsec < 0 || ts->tv_nsec >= NSEC_PER_SEC)
-		return -EINVAL;
-
 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
 	write_seqcount_begin(&tk_core.seq);
 
@@ -2321,6 +2318,9 @@ int do_adjtimex(struct __kernel_timex *txc)
 
 	if (txc->modes & ADJ_SETOFFSET) {
 		struct timespec64 delta;
+
+		if (txc->time.tv_usec < 0 || txc->time.tv_usec >= USEC_PER_SEC)
+			return -EINVAL;
 		delta.tv_sec  = txc->time.tv_sec;
 		delta.tv_nsec = txc->time.tv_usec;
 		if (!(txc->modes & ADJ_NANO))
-- 
2.7.4