linux-kernel - [PATCH v1 1/1] usb: gadget: f_fs: Stop ffs

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Date:   Thu, 8 Sep 2016 11:18:16 +0200
From:   Harish Jenny K N <harish_kandiga@...tor.com>
To:     Felipe Balbi <balbi@...nel.org>
CC:     <linux-usb@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-kernel@...r.kernel.org>, Jim Baxter <jim_baxter@...tor.com>
Subject: [PATCH v1 1/1] usb: gadget: f_fs: Stop ffs_closed NULL pointers.

From: Jim Baxter <jim_baxter@...tor.com>

The struct ffs_data::private_data has a pointer to
ffs_dev stored in it during the ffs_fs_mount() function
however it is not cleared when the ffs_dev is freed
later which causes the ffs_closed function to crash
with "Unable to handle kernel NULL pointer dereference"
error when using the data in ffs_data::private_data.

This clears this pointer during the ffs_free_dev clean
up function.

Signed-off-by: Jim Baxter <jim_baxter@...tor.com>
Signed-off-by: Jiada Wang <jiada_wang@...tor.com>
Signed-off-by: Harish Jenny K N <harish_kandiga@...tor.com>
---
 drivers/usb/gadget/function/f_fs.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 5c8429f..b309650 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -3470,6 +3470,11 @@ static void _ffs_free_dev(struct ffs_dev *dev)
 	list_del(&dev->entry);
 	if (dev->name_allocated)
 		kfree(dev->name);
+
+	/* Clear the private_data pointer to stop incorrect dev access */
+	if (dev->ffs_data)
+		dev->ffs_data->private_data = NULL;
+
 	kfree(dev);
 	if (list_empty(&ffs_devices))
 		functionfs_cleanup();
-- 
1.7.9.5