linux-kernel - [PATCH 5.4 01/71] firmware: arm_scpi: Prevent the ternary sign expansion bug

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Date:   Mon, 24 May 2021 17:25:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Cristian Marussi <cristian.marussi@....com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 01/71] firmware: arm_scpi: Prevent the ternary sign expansion bug

From: Dan Carpenter <dan.carpenter@...cle.com>

[ Upstream commit d9cd78edb2e6b7e26747c0ec312be31e7ef196fe ]

How the 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.

Link: https://lore.kernel.org/r/YIE7pdqV/h10tEAK@mwanda
Fixes: 8cb7cf56c9fe ("firmware: add support for ARM System Control and Power Interface(SCPI) protocol")
Reviewed-by: Cristian Marussi <cristian.marussi@....com>
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
[sudeep.holla: changed to return 0 as clock rate on error]
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 a80c331c3a6e..e2995ec14401 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 0;
 
-	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