Re: [PATCH] intel-agp.c: Fix crash when accessing nonexistent GTT entries in i915

[Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>]

On Wed, Mar 24, 2010 at 7:14 PM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Tue, 23 Mar 2010 12:40:05 +0100
> Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote:
>
>> On Tue, Mar 23, 2010 at 5:14 AM, Christian Kujau <lists@nerdbynature.de> wrote:
>> > On Mon, 22 Mar 2010 at 20:57, Andrew Morton wrote:
>> >> On Sun, 21 Mar 2010 16:30:20 +0100 Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote:
>> >> > I bisected in order to find the commit 5877960869333e42ebeb733e8d9d5630ff96d350.
>> >
>> > I believe this[0] is fc61901373987ad61851ed001fe971f3ee8d96a3 upstream:
>>
>> Indeed. Also in
>>
>> http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.32.y.git;a=commit;h=fc61901373987ad61851ed001fe971f3ee8d96a3
>
> Does reverting that patch from the current code fix the crash?

Yes. In addition, applying the patch I provided also fixes it in current code.

Current code:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=01e77706cdde7c0b47e5ca1f4284a795504c7c40

>
> --- a/drivers/char/agp/intel-agp.c~revert-1
> +++ a/drivers/char/agp/intel-agp.c
> @@ -207,7 +207,6 @@ static struct _intel_private {
>         * popup and for the GTT.
>         */
>        int gtt_entries;                        /* i830+ */
> -       int gtt_total_size;
>        union {
>                void __iomem *i9xx_flush_page;
>                void *i8xx_flush_page;
> @@ -1239,7 +1238,7 @@ static int intel_i915_configure(void)
>        readl(intel_private.registers+I810_PGETBL_CTL); /* PCI Posting. */
>
>        if (agp_bridge->driver->needs_scratch_page) {
> -               for (i = intel_private.gtt_entries; i < intel_private.gtt_total_size; i++) {
> +               for (i = intel_private.gtt_entries; i < current_size->num_entries; i++) {
>                        writel(agp_bridge->scratch_page, intel_private.gtt+i);
>                }
>                readl(intel_private.gtt+i-1);   /* PCI Posting. */
> @@ -1394,8 +1393,6 @@ static int intel_i915_create_gatt_table(
>        if (!intel_private.gtt)
>                return -ENOMEM;
>
> -       intel_private.gtt_total_size = gtt_map_size / 4;
> -
>        temp &= 0xfff80000;
>
>        intel_private.registers = ioremap(temp, 128 * 4096);
> @@ -1485,8 +1482,6 @@ static int intel_i965_create_gatt_table(
>        if (!intel_private.gtt)
>                return -ENOMEM;
>
> -       intel_private.gtt_total_size = gtt_size / 4;
> -
>        intel_private.registers = ioremap(temp, 128 * 4096);
>        if (!intel_private.registers) {
>                iounmap(intel_private.gtt);
> _
>
>