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Date: Mon, 13 Jul 2015 07:56:10 +0200 From: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com> To: Linus Torvalds <torvalds@...ux-foundation.org>, Jörg Otte <jrg.otte@...il.com>, Daniel Vetter <daniel.vetter@...ll.ch> CC: David Airlie <airlied@...ux.ie>, DRI <dri-devel@...ts.freedesktop.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference Op 12-07-15 om 18:52 schreef Linus Torvalds: > On Sun, Jul 12, 2015 at 1:03 AM, Jörg Otte <jrg.otte@...il.com> wrote: >> BUG: unable to handle kernel NULL pointer dereference at 0000000000000009 >> IP: [<ffffffffbd3447bb>] 0xffffffffbd3447bb > Ugh. Please enable KALLSYMS to get sane symbols. > > But yes, "crtc_state->base.active" is at offset 9 from "crtc_state", > so it's pretty clearly just that change frm > > - if (intel_crtc->active) { > + if (crtc_state->base.active) { > > and "crtc_state" is NULL. > > And the code very much knows that crtc_state can be NULL, since it's > initialized with > > crtc_state = state->base.state ? > intel_atomic_get_crtc_state(state->base.state, > intel_crtc) : NULL; > > Tssk. Daniel? Should I just revert that commit dec4f799d0a4 > ("drm/i915: Use crtc_state->active in primary check_plane func") for > now, or is there a better fix? Like just checking crtc_state for NULL? > > Linus More symbols would be nice. With the transitional helpers when crtc_state == NULL you don't want to update the scalers or funny things happen. Fix is probably something like this: diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index ba9321998a41..830e07b23a15 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -13276,7 +13276,7 @@ intel_check_primary_plane(struct drm_plane *plane, if (ret) return ret; - if (crtc_state->base.active) { + if (crtc_state ? crtc_state->base.active || crtc->state->active) { struct intel_plane_state *old_state = to_intel_plane_state(plane->state); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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