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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, Michael Mera <dev@michaelmera.com>,
        Leon Romanovsky <leonro@mellanox.com>,
        Doug Ledford <dledford@redhat.com>,
        Amit Pundir <amit.pundir@linaro.org>
Subject: [PATCH 4.4 15/43] IB/ocrdma: fix out of bounds access to local buffer
Date:   Tue, 14 Aug 2018 19:17:51 +0200
Message-Id: <20180814171518.106262417@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Mera <dev@michaelmera.com>

commit 062d0f22a30c39840ea49b72cfcfc1aa4cc538fa upstream.

In write to debugfs file 'resource_stats' the local buffer 'tmp_str' is
written at index 'count-1' where 'count' is the size of the write, so
potentially 0.

This patch filters odd values for the write size/position to avoid this
type of problem.

Signed-off-by: Michael Mera <dev@michaelmera.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/infiniband/hw/ocrdma/ocrdma_stats.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/infiniband/hw/ocrdma/ocrdma_stats.c
+++ b/drivers/infiniband/hw/ocrdma/ocrdma_stats.c
@@ -643,7 +643,7 @@ static ssize_t ocrdma_dbgfs_ops_write(st
 	struct ocrdma_stats *pstats = filp->private_data;
 	struct ocrdma_dev *dev = pstats->dev;
 
-	if (count > 32)
+	if (*ppos != 0 || count == 0 || count > sizeof(tmp_str))
 		goto err;
 
 	if (copy_from_user(tmp_str, buffer, count))