linux-kernel - [PATCH] firmware: arm_scpi: prevent ternary sign expansion bug

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Date:   Thu, 22 Apr 2021 12:02:29 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Cristian Marussi <cristian.marussi@....com>,
        "Jon Medhurst (Tixy)" <tixy@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] firmware: arm_scpi: prevent ternary sign expansion bug

How type promotion works in ternary expressions is a bit tricky.
The problem is that scpi_clk_get_val() returns longs, "ret" is a int
which holds a negative error code, and le32_to_cpu() is an unsigned int.
We want the negative error code to be cast to a negative long.  But
because le32_to_cpu() is an u32 then "ret" is type promoted to u32 and
becomes a high positive and then it is promoted to long and it is still
a high positive value.

Fix this by getting rid of the ternary.

Fixes: 8cb7cf56c9fe ("firmware: add support for ARM System Control and Power Interface(SCPI) protocol")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 drivers/firmware/arm_scpi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scpi.c b/drivers/firmware/arm_scpi.c
index d0dee37ad522..3bf61854121d 100644
--- a/drivers/firmware/arm_scpi.c
+++ b/drivers/firmware/arm_scpi.c
@@ -552,8 +552,10 @@ static unsigned long scpi_clk_get_val(u16 clk_id)
 
 	ret = scpi_send_message(CMD_GET_CLOCK_VALUE, &le_clk_id,
 				sizeof(le_clk_id), &rate, sizeof(rate));
+	if (ret)
+		return ret;
 
-	return ret ? ret : le32_to_cpu(rate);
+	return le32_to_cpu(rate);
 }
 
 static int scpi_clk_set_val(u16 clk_id, unsigned long rate)
-- 
2.30.2