This is a note to let you know that I've just added the patch titled
ptp_qoriq: fix overflow in ptp_qoriq_adjfine() u64 calcalation
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ptp_qoriq-fix-overflow-in-ptp_qoriq_adjfine-u64-calc.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 3d577212f65b5b354f372b3298ff59010d916bf3
Author: Yangbo Lu <yangbo.lu@xxxxxxx>
Date: Tue Mar 23 16:02:29 2021 +0800
ptp_qoriq: fix overflow in ptp_qoriq_adjfine() u64 calcalation
[ 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@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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;
