netdev - [PATCH net] net: stmmac: prevent division by 0 in stmmac_init_tstamp

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Message-ID: <58116e65-1bca-4d87-b165-78989e1aa195@omp.ru>
Date: Fri, 5 Sep 2025 19:06:50 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: 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>, Alexandre Torgue <alexandre.torgue@...s.st.com>,
	<netdev@...r.kernel.org>, <linux-stm32@...md-mailman.stormreply.com>
CC: <linux-arm-kernel@...ts.infradead.org>
Subject: [PATCH net] net: stmmac: prevent division by 0 in
 stmmac_init_tstamp_counter()

In stmmac_init_tstamp_counter(), the sec_inc variable is initialized to 0,
and if stmmac_config_sub_second_increment() fails to set it to some non-0
value, the following div_u64() call would cause a kernel oops (because of
the divide error exception).  Let's check sec_inc for 0 before dividing by
it and just return -EINVAL if so...

Found by Linux Verification Center (linuxtesting.org) with the Svace static
analysis tool.

Fixes: df103170854e ("net: stmmac: Avoid sometimes uninitialized Clang warnings")
Signed-off-by: Sergey Shtylyov <s.shtylyov@....ru>

---
The patch is against the master branch of Linus Torvalds' linux.git repo.

 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |    2 ++
 1 file changed, 2 insertions(+)

Index: linux/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
===================================================================
--- linux.orig/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ linux/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -817,6 +817,8 @@ int stmmac_init_tstamp_counter(struct st
 	stmmac_config_sub_second_increment(priv, priv->ptpaddr,
 					   priv->plat->clk_ptp_rate,
 					   xmac, &sec_inc);
+	if (!sec_inc)
+		return -EINVAL;
 	temp = div_u64(1000000000ULL, sec_inc);
 
 	/* Store sub second increment for later use */