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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Nathan Chancellor <natechancellor@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Julian Wiedmann <jwi@linux.ibm.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 23/51] s390: ctcm: fix ctcm_new_device error return code
Date:   Wed, 15 May 2019 12:55:58 +0200
Message-Id: <20190515090623.961966830@linuxfoundation.org>
In-Reply-To: <20190515090616.669619870@linuxfoundation.org>
References: <20190515090616.669619870@linuxfoundation.org>
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[ Upstream commit 27b141fc234a3670d21bd742c35d7205d03cbb3a ]

clang points out that the return code from this function is
undefined for one of the error paths:

../drivers/s390/net/ctcm_main.c:1595:7: warning: variable 'result' is used uninitialized whenever 'if' condition is true
      [-Wsometimes-uninitialized]
                if (priv->channel[direction] == NULL) {
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../drivers/s390/net/ctcm_main.c:1638:9: note: uninitialized use occurs here
        return result;
               ^~~~~~
../drivers/s390/net/ctcm_main.c:1595:3: note: remove the 'if' if its condition is always false
                if (priv->channel[direction] == NULL) {
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../drivers/s390/net/ctcm_main.c:1539:12: note: initialize the variable 'result' to silence this warning
        int result;
                  ^

Make it return -ENODEV here, as in the related failure cases.
gcc has a known bug in underreporting some of these warnings
when it has already eliminated the assignment of the return code
based on some earlier optimization step.

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/s390/net/ctcm_main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/s390/net/ctcm_main.c b/drivers/s390/net/ctcm_main.c
index ad17fc5883f61..e22b9ac3e564f 100644
--- a/drivers/s390/net/ctcm_main.c
+++ b/drivers/s390/net/ctcm_main.c
@@ -1595,6 +1595,7 @@ static int ctcm_new_device(struct ccwgroup_device *cgdev)
 		if (priv->channel[direction] == NULL) {
 			if (direction == CTCM_WRITE)
 				channel_free(priv->channel[CTCM_READ]);
+			result = -ENODEV;
 			goto out_dev;
 		}
 		priv->channel[direction]->netdev = dev;
-- 
2.20.1