2018-01-22 16:00:49

by Niklas Cassel

Subject: [PATCH net-next] net: stmmac: do not use a bitwise AND operator with a bool operand

Doing a bitwise AND between a bool and an int is generally not a good idea.
The bool will be promoted to an int with value 0 or 1,
the int is generally regarded as true with a non-zero value,
thus ANDing them has the potential to yield an undesired result.

This commit fixes the following smatch warnings:

drivers/net/ethernet/stmicro/stmmac/enh_desc.c:344 enh_desc_prepare_tx_desc() warn: maybe use && instead of &
drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c:337 dwmac4_rd_prepare_tx_desc() warn: maybe use && instead of &
drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c:380 dwmac4_rd_prepare_tso_tx_desc() warn: maybe use && instead of &

Signed-off-by: Niklas Cassel <[email protected]>
---
drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c | 4 ++--
drivers/net/ethernet/stmicro/stmmac/enh_desc.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
index 2fd8456999f6..c728ffa095de 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
@@ -334,7 +334,7 @@ static void dwmac4_rd_prepare_tx_desc(struct dma_desc *p, int is_fs, int len,
if (tx_own)
tdes3 |= TDES3_OWN;

- if (is_fs & tx_own)
+ if (is_fs && tx_own)
/* When the own bit, for the first frame, has to be set, all
* descriptors for the same frame has to be set before, to
* avoid race condition.
@@ -377,7 +377,7 @@ static void dwmac4_rd_prepare_tso_tx_desc(struct dma_desc *p, int is_fs,
if (tx_own)
tdes3 |= TDES3_OWN;

- if (is_fs & tx_own)
+ if (is_fs && tx_own)
/* When the own bit, for the first frame, has to be set, all
* descriptors for the same frame has to be set before, to
* avoid race condition.
diff --git a/drivers/net/ethernet/stmicro/stmmac/enh_desc.c b/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
index b47cb5c4da51..6768a25b6aa0 100644
--- a/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
+++ b/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
@@ -341,7 +341,7 @@ static void enh_desc_prepare_tx_desc(struct dma_desc *p, int is_fs, int len,
if (tx_own)
tdes0 |= ETDES0_OWN;

- if (is_fs & tx_own)
+ if (is_fs && tx_own)
/* When the own bit, for the first frame, has to be set, all
* descriptors for the same frame has to be set before, to
* avoid race condition.
--
2.14.2

2018-01-24 21:29:34

by David Miller

Subject: Re: [PATCH net-next] net: stmmac: do not use a bitwise AND operator with a bool operand

From: Niklas Cassel <[email protected]>
Date: Mon, 22 Jan 2018 16:59:50 +0100

> Doing a bitwise AND between a bool and an int is generally not a good idea.
> The bool will be promoted to an int with value 0 or 1,
> the int is generally regarded as true with a non-zero value,
> thus ANDing them has the potential to yield an undesired result.
>
> This commit fixes the following smatch warnings:
>
> drivers/net/ethernet/stmicro/stmmac/enh_desc.c:344 enh_desc_prepare_tx_desc() warn: maybe use && instead of &
> drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c:337 dwmac4_rd_prepare_tx_desc() warn: maybe use && instead of &
> drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c:380 dwmac4_rd_prepare_tso_tx_desc() warn: maybe use && instead of &
>
> Signed-off-by: Niklas Cassel <[email protected]>

Applied.