linux-kernel - [PATCH AUTOSEL 5.2 108/185] PM / devfreq: Fix kernel oops on governor module load

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Message-Id: <20190922184924.32534-108-sashal@kernel.org>
Date:   Sun, 22 Sep 2019 14:48:06 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ezequiel Garcia <ezequiel@...labora.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Sasha Levin <sashal@...nel.org>, linux-pm@...r.kernel.org
Subject: [PATCH AUTOSEL 5.2 108/185] PM / devfreq: Fix kernel oops on governor module load

From: Ezequiel Garcia <ezequiel@...labora.com>

[ Upstream commit 7544fd7f384591038646d3cd9efb311ab4509e24 ]

A bit unexpectedly (but still documented), request_module may
return a positive value, in case of a modprobe error.
This is currently causing issues in the devfreq framework.

When a request_module exits with a positive value, we currently
return that via ERR_PTR. However, because the value is positive,
it's not a ERR_VALUE proper, and is therefore treated as a
valid struct devfreq_governor pointer, leading to a kernel oops.

Fix this by returning -EINVAL if request_module returns a positive
value.

Fixes: b53b0128052ff ("PM / devfreq: Fix static checker warning in try_then_request_governor")
Signed-off-by: Ezequiel Garcia <ezequiel@...labora.com>
Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@...sung.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/devfreq/devfreq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index ab22bf8a12d69..a0e19802149fc 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -254,7 +254,7 @@ static struct devfreq_governor *try_then_request_governor(const char *name)
 		/* Restore previous state before return */
 		mutex_lock(&devfreq_list_lock);
 		if (err)
-			return ERR_PTR(err);
+			return (err < 0) ? ERR_PTR(err) : ERR_PTR(-EINVAL);
 
 		governor = find_devfreq_governor(name);
 	}
-- 
2.20.1