linux-kernel - [PATCH AUTOSEL for 4.15 131/189] IB/hfi1: Fix for potential refcount leak in hfi1_open

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Date:   Mon, 9 Apr 2018 00:18:31 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Alex Estrin <alex.estrin@...el.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.15 131/189] IB/hfi1: Fix for potential refcount
 leak in hfi1_open_file()

From: Alex Estrin <alex.estrin@...el.com>

[ Upstream commit 2b1e7fe16124e86ee9242aeeee859c79a843e3a2 ]

The dd refcount is speculatively incremented prior to allocating
the fd memory with kzalloc(). If that kzalloc() failed the dd
refcount leaks.
Increment refcount on kzalloc success.

Fixes: e11ffbd57520 ("IB/hfi1: Do not free hfi1 cdev parent structure early")
Reviewed-by: Michael J Ruhl <michael.j.ruhl@...el.com>
Signed-off-by: Alex Estrin <alex.estrin@...el.com>
Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/infiniband/hw/hfi1/file_ops.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/file_ops.c b/drivers/infiniband/hw/hfi1/file_ops.c
index 1df7da47f431..acf0ba56c309 100644
--- a/drivers/infiniband/hw/hfi1/file_ops.c
+++ b/drivers/infiniband/hw/hfi1/file_ops.c
@@ -196,9 +196,6 @@ static int hfi1_file_open(struct inode *inode, struct file *fp)
 	if (!atomic_inc_not_zero(&dd->user_refcount))
 		return -ENXIO;
 
-	/* Just take a ref now. Not all opens result in a context assign */
-	kobject_get(&dd->kobj);
-
 	/* The real work is performed later in assign_ctxt() */
 
 	fd = kzalloc(sizeof(*fd), GFP_KERNEL);
@@ -208,6 +205,7 @@ static int hfi1_file_open(struct inode *inode, struct file *fp)
 		fd->mm = current->mm;
 		mmgrab(fd->mm);
 		fd->dd = dd;
+		kobject_get(&fd->dd->kobj);
 		fp->private_data = fd;
 	} else {
 		fp->private_data = NULL;
-- 
2.15.1