[PATCH 5.10/5.15/6.1/6.6] net: stmmac: make sure that ptp_rate is not 0 before configuring EST

[PATCH 5.10/5.15/6.1/6.6] net: stmmac: make sure that ptp_rate is not 0 before configuring EST

[Vasiliy Kovalev]

From: Alexis Lothoré <alexis.lothore@bootlin.com>

commit cbefe2ffa7784525ec5d008ba87c7add19ec631a upstream.

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@bootlin.com>
Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Fixes: 8572aec3d0dc ("net: stmmac: Add basic EST support for XGMAC")
Link: https://patch.msgid.link/20250529-stmmac_tstamp_div-v4-2-d73340a794d5@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ kovalev: bp to fix CVE-2025-38125;
  replaced netdev_warn with pr_warn due to missing dev pointer ]
Signed-off-by: Vasiliy Kovalev <kovalev@altlinux.org>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac5.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
index 8fd167501fa0..4df62268f852 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
@@ -597,6 +597,11 @@ int dwmac5_est_configure(void __iomem *ioaddr, struct stmmac_est *cfg,
 	int i, ret = 0x0;
 	u32 ctrl;
 
+	if (!ptp_rate) {
+		pr_warn("%s: Invalid PTP rate\n", __func__);
+		return -EINVAL;
+	}
+
 	ret |= dwmac5_est_write(ioaddr, BTR_LOW, cfg->btr[0], false);
 	ret |= dwmac5_est_write(ioaddr, BTR_HIGH, cfg->btr[1], false);
 	ret |= dwmac5_est_write(ioaddr, TER, cfg->ter, false);
-- 
2.50.1