linux-kernel - [151/197] agp/hp: fixup hp agp after ACPI changes

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Date:	Thu, 22 Apr 2010 12:10:02 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Dave Airlie <airlied@...hat.com>
Subject: [151/197] agp/hp: fixup hp agp after ACPI changes

2.6.32-stable review patch.  If anyone has any objections, please let us know.

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

From: Bjorn Helgaas <bjorn.helgaas@...com>

commit 67fe63b0715ccfaefa0af8a6e705c5470ee5cada upstream.

Commit 15b8dd53f5ffa changed the string in info->hardware_id from a static
array to a pointer and added a length field.  But instead of changing
"sizeof(array)" to "length", we changed it to "sizeof(length)" (== 4),
which corrupts the string we're trying to null-terminate.

We no longer even need to null-terminate the string, but we *do* need to
check whether we found a HID.  If there's no HID, we used to have an empty
array, but now we have a null pointer.

The combination of these defects causes this oops:

  Unable to handle kernel NULL pointer dereference (address 0000000000000003)
  modprobe[895]: Oops 8804682956800 [1]
  ip is at zx1_gart_probe+0xd0/0xcc0 [hp_agp]

  http://marc.info/?l=linux-ia64&m=126264484923647&w=2

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@...com>
Reported-by: Émeric Maschino <emeric.maschino@...il.com>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/char/agp/hp-agp.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/char/agp/hp-agp.c
+++ b/drivers/char/agp/hp-agp.c
@@ -488,9 +488,8 @@ zx1_gart_probe (acpi_handle obj, u32 dep
 	handle = obj;
 	do {
 		status = acpi_get_object_info(handle, &info);
-		if (ACPI_SUCCESS(status)) {
+		if (ACPI_SUCCESS(status) && (info->valid & ACPI_VALID_HID)) {
 			/* TBD check _CID also */
-			info->hardware_id.string[sizeof(info->hardware_id.length)-1] = '\0';
 			match = (strcmp(info->hardware_id.string, "HWP0001") == 0);
 			kfree(info);
 			if (match) {


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