[ 3.8.y.z extended stable ] Patch "HID: picolcd: Prevent NULL pointer dereference on _remove()" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    HID: picolcd: Prevent NULL pointer dereference on _remove()

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.10.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From 8adbf5f92347f9a35335126d64cf0b119173c248 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bruno=20Pr=C3=A9mont?= <bonbons at linux-vserver.org>
Date: Sat, 31 Aug 2013 14:07:48 +0200
Subject: HID: picolcd: Prevent NULL pointer dereference on _remove()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit 1cde501bb4655e98fb832194beb88ac73be5a05d upstream.

When picolcd is switched into bootloader mode (for FW flashing) make
sure not to try to dereference NULL-pointers of feature-devices during
unplug/unbind.

This fixes following BUG:
  BUG: unable to handle kernel NULL pointer dereference at 00000298
  IP: [<f811f56b>] picolcd_exit_framebuffer+0x1b/0x80 [hid_picolcd]
  *pde = 00000000
  Oops: 0000 [#1]
  Modules linked in: hid_picolcd syscopyarea sysfillrect sysimgblt fb_sys_fops
  CPU: 0 PID: 15 Comm: khubd Not tainted 3.11.0-rc7-00002-g50d62d4 #2
  EIP: 0060:[<f811f56b>] EFLAGS: 00010292 CPU: 0
  EIP is at picolcd_exit_framebuffer+0x1b/0x80 [hid_picolcd]
  Call Trace:
   [<f811d1ab>] picolcd_remove+0xcb/0x120 [hid_picolcd]
   [<c1469b09>] hid_device_remove+0x59/0xc0
   [<c13464ca>] __device_release_driver+0x5a/0xb0
   [<c134653f>] device_release_driver+0x1f/0x30
   [<c134603d>] bus_remove_device+0x9d/0xd0
   [<c13439a5>] device_del+0xd5/0x150
   [<c14696a4>] hid_destroy_device+0x24/0x60
   [<c1474cbb>] usbhid_disconnect+0x1b/0x40
   ...

Signed-off-by: Bruno Prémont <bonbons at linux-vserver.org>
Signed-off-by: Jiri Kosina <jkosina at suse.cz>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/hid/hid-picolcd_cir.c | 3 ++-
 drivers/hid/hid-picolcd_fb.c  | 6 +++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-picolcd_cir.c b/drivers/hid/hid-picolcd_cir.c
index a79e95b..1a79a1e 100644
--- a/drivers/hid/hid-picolcd_cir.c
+++ b/drivers/hid/hid-picolcd_cir.c
@@ -147,6 +147,7 @@ void picolcd_exit_cir(struct picolcd_data *data)
 	struct rc_dev *rdev = data->rc_dev;

 	data->rc_dev = NULL;
-	rc_unregister_device(rdev);
+	if (rdev)
+		rc_unregister_device(rdev);
 }

diff --git a/drivers/hid/hid-picolcd_fb.c b/drivers/hid/hid-picolcd_fb.c
index eb00357..104df56 100644
--- a/drivers/hid/hid-picolcd_fb.c
+++ b/drivers/hid/hid-picolcd_fb.c
@@ -595,10 +595,14 @@ err_nomem:
 void picolcd_exit_framebuffer(struct picolcd_data *data)
 {
 	struct fb_info *info = data->fb_info;
-	struct picolcd_fb_data *fbdata = info->par;
+	struct picolcd_fb_data *fbdata;
 	unsigned long flags;

+	if (!info)
+		return;
+
 	device_remove_file(&data->hdev->dev, &dev_attr_fb_update_rate);
+	fbdata = info->par;

 	/* disconnect framebuffer from HID dev */
 	spin_lock_irqsave(&fbdata->lock, flags);
--
1.8.1.2