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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, Frank de Brabander <debrabander@gmail.com>,
        Willem de Bruijn <willemb@google.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 5.1 36/62] selftests: txring_overwrite: fix incorrect test of mmap() return value
Date:   Fri, 26 Jul 2019 17:24:48 +0200
Message-Id: <20190726152305.730113051@linuxfoundation.org>
In-Reply-To: <20190726152301.720139286@linuxfoundation.org>
References: <20190726152301.720139286@linuxfoundation.org>
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From: Frank de Brabander <debrabander@gmail.com>

[ Upstream commit cecaa76b2919aac2aa584ce476e9fcd5b084add5 ]

If mmap() fails it returns MAP_FAILED, which is defined as ((void *) -1).
The current if-statement incorrectly tests if *ring is NULL.

Fixes: 358be656406d ("selftests/net: add txring_overwrite")
Signed-off-by: Frank de Brabander <debrabander@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 tools/testing/selftests/net/txring_overwrite.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/testing/selftests/net/txring_overwrite.c
+++ b/tools/testing/selftests/net/txring_overwrite.c
@@ -113,7 +113,7 @@ static int setup_tx(char **ring)
 
 	*ring = mmap(0, req.tp_block_size * req.tp_block_nr,
 		     PROT_READ | PROT_WRITE, MAP_SHARED, fdt, 0);
-	if (!*ring)
+	if (*ring == MAP_FAILED)
 		error(1, errno, "mmap");
 
 	return fdt;