[PATCH] time: adjtimex: validate the ADJ_FREQUENCY case

[Sasha Levin]

Verify that the frequency value from userspace is valid and makes sense.

Unverified values can cause overflows later on.

Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
 kernel/time/ntp.c |    9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 87a346f..54828cf 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -633,6 +633,15 @@ int ntp_validate_timex(struct timex *txc)
 	if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME)))
 		return -EPERM;
 
+	if (txc->modes & ADJ_FREQUENCY) {
+		if (!capable(CAP_SYS_TIME))
+			return -EPERM;
+		if (txc->freq < 0)
+			return -EINVAL;
+		if (LONG_MAX / PPM_SCALE < txc->freq)
+			return -EINVAL;
+	}
+
 	return 0;
 }
 
-- 
1.7.10.4

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