linux-kernel - [PATCH 4.4 230/312] power: test_power: correctly handle empty writes

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Message-Id: <20200508123140.616507722@linuxfoundation.org>
Date:   Fri,  8 May 2020 14:33:41 +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, Sasha Levin <sasha.levin@...cle.com>,
        Sebastian Reichel <sre@...nel.org>
Subject: [PATCH 4.4 230/312] power: test_power: correctly handle empty writes

From: Sasha Levin <sasha.levin@...cle.com>

commit 6b9140f39c2aaf76791197fbab0839c0e4af56e8 upstream.

Writing 0 length data into test_power makes it access an invalid array
location and kill the system.

Fixes: f17ef9b2d ("power: Make test_power driver more dynamic.")
Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
Signed-off-by: Sebastian Reichel <sre@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/power/test_power.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/power/test_power.c
+++ b/drivers/power/test_power.c
@@ -301,6 +301,8 @@ static int map_get_value(struct battery_
 	buf[MAX_KEYLENGTH-1] = '\0';
 
 	cr = strnlen(buf, MAX_KEYLENGTH) - 1;
+	if (cr < 0)
+		return def_val;
 	if (buf[cr] == '\n')
 		buf[cr] = '\0';