[tip:timers/urgent] time: adjtimex: Validate the ADJ_FREQUENCY values

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Commit-ID:  5e5aeb4367b450a28f447f6d5ab57d8f2ab16a5f
Gitweb:     http://git.kernel.org/tip/5e5aeb4367b450a28f447f6d5ab57d8f2ab16a5f
Author:     Sasha Levin <sasha.levin@xxxxxxxxxx>
AuthorDate: Wed, 3 Dec 2014 19:25:05 -0500
Committer:  John Stultz <john.stultz@xxxxxxxxxx>
CommitDate: Wed, 7 Jan 2015 09:50:32 -0800

time: adjtimex: Validate the ADJ_FREQUENCY values

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

Unverified values can cause overflows later on.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
[jstultz: Fix up bug for negative values and drop redunent cap check]
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
 kernel/time/ntp.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 87a346f..28bf91c 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -633,6 +633,13 @@ int ntp_validate_timex(struct timex *txc)
 	if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME)))
 		return -EPERM;
 
+	if (txc->modes & ADJ_FREQUENCY) {
+		if (LONG_MIN / PPM_SCALE > txc->freq)
+			return -EINVAL;
+		if (LONG_MAX / PPM_SCALE < txc->freq)
+			return -EINVAL;
+	}
+
 	return 0;
 }
 
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