Re: [PATCH v2] net: stmmac: Fix possible division by zero
flat view
From: Leon Romanovsky <leon@kernel.org>
Date: 2021-12-07 08:31:51
Also in:
lkml
Subsystem:
networking drivers, stmmac ethernet driver, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Maxime Chevallier, Linus Torvalds
On Mon, Dec 06, 2021 at 07:23:37PM +0500, Ameer Hamza wrote:
quoted hunk ↗ jump to hunk
In stmmac_init_tstamp_counter() routine, there is a possiblity of division by zero. If priv->plat->clk_ptp_rate becomes greater than 1 GHz, config_sub_second_increment() subroutine may calculate sec_inc as zero depending upon the PTP_TCR_TSCFUPDT register value, which will cause divide by zero exception. Fixes: a6da2bbb0005e ("net: stmmac: retain PTP clock time during SIOCSHWTSTAMP ioctls") Addresses-Coverity: 1494557 ("Division or modulo by zero") Signed-off-by: Ameer Hamza <redacted> --- Changes in v2: Added fix tag, bug justification, and commit author. --- drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c index da8306f60730..f44400323407 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c@@ -863,7 +863,7 @@ int stmmac_init_tstamp_counter(struct stmmac_priv *priv, u32 systime_flags) stmmac_config_sub_second_increment(priv, priv->ptpaddr, priv->plat->clk_ptp_rate, xmac, &sec_inc); - temp = div_u64(1000000000ULL, sec_inc); + temp = div_u64(1000000000ULL, (sec_inc > 0) ? sec_inc : 1);
It can be written cleanly with max(a,b):
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 4e05c1d92935..e2e232bff511 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c@@ -855,7 +855,7 @@ int stmmac_init_tstamp_counter(struct stmmac_priv *priv, u32 systime_flags) stmmac_config_sub_second_increment(priv, priv->ptpaddr, priv->plat->clk_ptp_rate, xmac, &sec_inc); - temp = div_u64(1000000000ULL, sec_inc); + temp = div_u64(1000000000ULL, max(sec_inc, 1)); /* Store sub second increment for later use */ priv->sub_second_inc = sec_inc;
/* Store sub second increment for later use */ priv->sub_second_inc = sec_inc; -- 2.25.1