Fw: Oops in hidinput_hid_event

[Pete Zaitcev <zaitcev@redhat.com>]

I think this patch is rather obvious, so maybe I should ask Andrew to
apply it to -mm for now, to get some testing. Would that help to verify
it for acceptance?

-- Pete

Begin forwarded message:

Date: Tue, 28 Jun 2005 15:00:23 -0700
From: Pete Zaitcev <zaitcev@redhat.com>
To: vojtech@suse.cz
Cc: zaitcev@redhat.com, linux-usb-devel@lists.sourceforge.net
Subject: Oops in hidinput_hid_event

Hi, Vojtech:

Someone reported a bug in Fedora, which runs a largely unmodified upstream
kernel in this area. Whenever the user hits a key which switches LED,
the system oopses. Here's a trace:

Unable to handle kernel NULL pointer dereference at virtual address 000000c8
EFLAGS: 00010006   (2.6.11-1.1369_FC4smp)
EIP is at hidinput_hid_event+0x2d/0x292                                       
Call Trace:           
 [<c02872e0>] hid_process_event+0x57/0x5f
 [<c028758a>] hid_input_field+0x2a2/0x2ac
 [<c0287632>] hid_input_report+0x9e/0xb8
 [<c0287f62>] hid_ctrl+0x14c/0x151
 [<e0a21060>] uhci_destroy_urb_priv+0xb5/0x10a [uhci_hcd]
 [<c027dab5>] usb_hcd_giveback_urb+0x24/0x67
 [<e0a22360>] uhci_finish_urb+0x2d/0x38 [uhci_hcd]
 [<e0a223af>] uhci_finish_completion+0x44/0x56 [uhci_hcd]
 [<e0a224a2>] uhci_scan_schedule+0xaa/0x13a [uhci_hcd]
 [<c023413d>] i8042_interrupt+0x121/0x234
 [<e0a226d0>] uhci_irq+0x47/0x10d [uhci_hcd]

Full trace at
 https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=160709

Any ideas?

By the way, it seems that I see a bug in hidinput_hid_event.
The check for NULL can never work, becaue &hidinput->input
is nonzero at all times. How about this?

--- linux-2.6.12/drivers/usb/input/hid-input.c	2005-06-21 12:58:47.000000000 -0700
+++ linux-2.6.12-lem/drivers/usb/input/hid-input.c	2005-06-28 14:57:22.000000000 -0700
@@ -397,11 +397,12 @@
 
 void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct hid_usage *usage, __s32 value, struct pt_regs *regs)
 {
-	struct input_dev *input = &field->hidinput->input;
+	struct input_dev *input;
 	int *quirks = &hid->quirks;
 
-	if (!input)
+	if (!field->hidinput)
 		return;
+	input = &field->hidinput->input;
 
 	input_regs(input, regs);
 

-- Pete