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Subject[PATCH 57/93] HID: picolcd: Prevent NULL pointer dereference on _remove()
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3.8.13.10 -stable review patch.  If anyone has any objections, please let me know.

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

From: =?UTF-8?q?Bruno=20Pr=C3=A9mont?= <bonbons@linux-vserver.org>

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@linux-vserver.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Kamal Mostafa <kamal@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
--
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