[PATCH] net: stmmac: gmac5+: fix potential integer overflow on 32 bit multiply

[PATCH] net: stmmac: gmac5+: fix potential integer overflow on 32 bit multiply

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

The multiplication of cfg->ctr[1] by 1000000000 is performed using a
32 bit multiplication (since cfg->ctr[1] is a u32) and this can lead
to a potential overflow. Fix this by making the constant a ULL to
ensure a 64 bit multiply occurs.

Fixes: 504723af0d85 ("net: stmmac: Add basic EST support for GMAC5+")
Addresses-Coverity: ("Unintentional integer overflow")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac5.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
index 494c859b4ade..67ba67ed0cb9 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
@@ -624,7 +624,7 @@ int dwmac5_est_configure(void __iomem *ioaddr, struct stmmac_est *cfg,
 		total_offset += offset;
 	}
 
-	total_ctr = cfg->ctr[0] + cfg->ctr[1] * 1000000000;
+	total_ctr = cfg->ctr[0] + cfg->ctr[1] * 1000000000ULL;
 	total_ctr += total_offset;
 
 	ctr_low = do_div(total_ctr, 1000000000);
-- 
2.25.1

Re: [PATCH] net: stmmac: gmac5+: fix potential integer overflow on 32 bit multiply

[David Miller]

From: Colin King <colin.king@canonical.com>
Date: Fri,  1 May 2020 15:10:16 +0100

> From: Colin Ian King <colin.king@canonical.com>
> 
> The multiplication of cfg->ctr[1] by 1000000000 is performed using a
> 32 bit multiplication (since cfg->ctr[1] is a u32) and this can lead
> to a potential overflow. Fix this by making the constant a ULL to
> ensure a 64 bit multiply occurs.
> 
> Fixes: 504723af0d85 ("net: stmmac: Add basic EST support for GMAC5+")
> Addresses-Coverity: ("Unintentional integer overflow")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

Applied.