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Message-Id: <20210329222222.2382987-25-sashal@kernel.org>
Date: Mon, 29 Mar 2021 18:22:13 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Yangbo Lu <yangbo.lu@....com>,
"David S . Miller" <davem@...emloft.net>,
Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.10 25/33] ptp_qoriq: fix overflow in ptp_qoriq_adjfine() u64 calcalation
From: Yangbo Lu <yangbo.lu@....com>
[ Upstream commit f51d7bf1dbe5522c51c93fe8faa5f4abbdf339cd ]
Current calculation for diff of TMR_ADD register value may have
64-bit overflow in this code line, when long type scaled_ppm is
large.
adj *= scaled_ppm;
This patch is to resolve it by using mul_u64_u64_div_u64().
Signed-off-by: Yangbo Lu <yangbo.lu@....com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
drivers/ptp/ptp_qoriq.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/drivers/ptp/ptp_qoriq.c b/drivers/ptp/ptp_qoriq.c
index beb5f74944cd..08f4cf0ad9e3 100644
--- a/drivers/ptp/ptp_qoriq.c
+++ b/drivers/ptp/ptp_qoriq.c
@@ -189,15 +189,16 @@ int ptp_qoriq_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
tmr_add = ptp_qoriq->tmr_add;
adj = tmr_add;
- /* calculate diff as adj*(scaled_ppm/65536)/1000000
- * and round() to the nearest integer
+ /*
+ * Calculate diff and round() to the nearest integer
+ *
+ * diff = adj * (ppb / 1000000000)
+ * = adj * scaled_ppm / 65536000000
*/
- adj *= scaled_ppm;
- diff = div_u64(adj, 8000000);
- diff = (diff >> 13) + ((diff >> 12) & 1);
+ diff = mul_u64_u64_div_u64(adj, scaled_ppm, 32768000000);
+ diff = DIV64_U64_ROUND_UP(diff, 2);
tmr_add = neg_adj ? tmr_add - diff : tmr_add + diff;
-
ptp_qoriq->write(®s->ctrl_regs->tmr_add, tmr_add);
return 0;
--
2.30.1
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