netdev - [PATCH v3 2/2] net: stmmac: make sure that ptp_rate is not 0 before configuring EST

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Message-Id: <20250528-stmmac_tstamp_div-v3-2-b525ecdfd84c@bootlin.com>
Date: Wed, 28 May 2025 10:29:51 +0200
From: Alexis Lothoré <alexis.lothore@...tlin.com>
To: Alexandre Torgue <alexandre.torgue@...s.st.com>, 
 Jose Abreu <joabreu@...opsys.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Maxime Coquelin <mcoquelin.stm32@...il.com>, 
 Richard Cochran <richardcochran@...il.com>, 
 Phil Reid <preid@...ctromag.com.au>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Maxime Chevallier <maxime.chevallier@...tlin.com>, netdev@...r.kernel.org, 
 linux-stm32@...md-mailman.stormreply.com, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Jose Abreu <Jose.Abreu@...opsys.com>, 
 Alexis Lothoré <alexis.lothore@...tlin.com>
Subject: [PATCH v3 2/2] net: stmmac: make sure that ptp_rate is not 0
 before configuring EST

If the ptp_rate recorded earlier in the driver happens to be 0, this
bogus value will propagate up to EST configuration, where it will
trigger a division by 0.

Prevent this division by 0 by adding the corresponding check and error
code.

Suggested-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
Signed-off-by: Alexis Lothoré <alexis.lothore@...tlin.com>
Fixes: 8572aec3d0dc ("net: stmmac: Add basic EST support for XGMAC")
---
Changes in v3:
- new patch
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_est.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_est.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_est.c
index c9693f77e1f61fe5c92f95f5e544371445626c4d..ac6f2e3a3fcd2f9ae21913845282ff015cd2f7ec 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_est.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_est.c
@@ -32,6 +32,11 @@ static int est_configure(struct stmmac_priv *priv, struct stmmac_est *cfg,
 	int i, ret = 0;
 	u32 ctrl;

+	if (!ptp_rate) {
+		netdev_warn(priv->dev, "Invalid PTP rate");
+		return -EINVAL;
+	}
+
 	ret |= est_write(est_addr, EST_BTR_LOW, cfg->btr[0], false);
 	ret |= est_write(est_addr, EST_BTR_HIGH, cfg->btr[1], false);
 	ret |= est_write(est_addr, EST_TER, cfg->ter, false);

-- 
2.49.0