linux-kernel - [PATCH] firmware: arm_scmi: Fix incorrect error propagation

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Date:   Fri, 10 Jun 2022 16:00:55 +0200
From:   Ludvig Pärsson <ludvig.parsson@...s.com>
To:     Sudeep Holla <sudeep.holla@....com>
CC:     <kernel@...s.com>,
        Ludvig Pärsson <ludvig.parsson@...s.com>,
        Cristian Marussi <cristian.marussi@....com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] firmware: arm_scmi: Fix incorrect error propagation

scmi_voltage_descriptors_get() will incorrecly return an
error code if the last iteration of the for loop that
retrieves the descriptors is skipped due to an error.
Skipping an iteration in the loop is not an error, but
the `ret` value from the last iteration will be
propagated when the function returns.

Fix by not saving return values that should not be
propagated. This solution also minimizes the risk of
future patches accidentally reintroducing this bug.

Signed-off-by: Ludvig Pärsson <ludvig.parsson@...s.com>
---
 drivers/firmware/arm_scmi/voltage.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/firmware/arm_scmi/voltage.c b/drivers/firmware/arm_scmi/voltage.c
index 9d195d8719ab..49b75375d3ff 100644
--- a/drivers/firmware/arm_scmi/voltage.c
+++ b/drivers/firmware/arm_scmi/voltage.c
@@ -225,9 +225,8 @@ static int scmi_voltage_descriptors_get(const struct scmi_protocol_handle *ph,
 
 		/* Retrieve domain attributes at first ... */
 		put_unaligned_le32(dom, td->tx.buf);
-		ret = ph->xops->do_xfer(ph, td);
 		/* Skip domain on comms error */
-		if (ret)
+		if (ph->xops->do_xfer(ph, td))
 			continue;
 
 		v = vinfo->domains + dom;
@@ -249,9 +248,8 @@ static int scmi_voltage_descriptors_get(const struct scmi_protocol_handle *ph,
 				v->async_level_set = true;
 		}
 
-		ret = scmi_voltage_levels_get(ph, v);
 		/* Skip invalid voltage descriptors */
-		if (ret)
+		if (scmi_voltage_levels_get(ph, v))
 			continue;
 
 		ph->xops->reset_rx_to_maxsz(ph, td);
-- 
2.20.1