linux-kernel - [PATCH 4.9 021/107] IB/ocrdma: fix out of bounds access to local buffer

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Date:   Tue, 14 Aug 2018 19:16:44 +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, Michael Mera <dev@...haelmera.com>,
        Leon Romanovsky <leonro@...lanox.com>,
        Doug Ledford <dledford@...hat.com>,
        Amit Pundir <amit.pundir@...aro.org>
Subject: [PATCH 4.9 021/107] IB/ocrdma: fix out of bounds access to local buffer

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Michael Mera <dev@...haelmera.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@...haelmera.com>
Reviewed-by: Leon Romanovsky <leonro@...lanox.com>
Signed-off-by: Doug Ledford <dledford@...hat.com>
Signed-off-by: Amit Pundir <amit.pundir@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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
@@ -645,7 +645,7 @@ 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))