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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, Rob Gardner <rob.gardner@oracle.com>,
        Jonathan Helman <jonathan.helman@oracle.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.16 10/68] [PATCH] sparc64: Properly range check DAX completion index
Date:   Tue, 17 Apr 2018 17:57:23 +0200
Message-Id: <20180417155749.752137992@linuxfoundation.org>
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4.16-stable review patch.  If anyone has any objections, please let me know.

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

From: Rob Gardner <rob.gardner@oracle.com>


[ Upstream commit 49d7006d9f01d435661d03bbea3db4c33935b3d8 ]

Each Oracle DAX CCB has a corresponding completion area, and the required
number of areas must fit within a previously allocated array of completion
areas beginning at the requested index.  Since the completion area index
is specified by a file offset, a user can pass arbitrary values, including
negative numbers. So the index must be thoroughly range checked to prevent
access to addresses outside the bounds of the allocated completion
area array.  The index cannot be negative, and it cannot exceed the
total array size, less the number of CCBs requested. The old code did
not check for negative values and was off by one on the upper bound.

Signed-off-by: Rob Gardner <rob.gardner@oracle.com>
Signed-off-by: Jonathan Helman <jonathan.helman@oracle.com>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/sbus/char/oradax.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/sbus/char/oradax.c
+++ b/drivers/sbus/char/oradax.c
@@ -880,7 +880,7 @@ static int dax_ccb_exec(struct dax_ctx *
 	dax_dbg("args: ccb_buf_len=%ld, idx=%d", count, idx);
 
 	/* for given index and length, verify ca_buf range exists */
-	if (idx + nccbs >= DAX_CA_ELEMS) {
+	if (idx < 0 || idx > (DAX_CA_ELEMS - nccbs)) {
 		ctx->result.exec.status = DAX_SUBMIT_ERR_NO_CA_AVAIL;
 		return 0;
 	}