From patchwork Wed Jul 29 13:09:12 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 11691001 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C0EED1392 for ; Wed, 29 Jul 2020 13:09:41 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A0B352083B for ; Wed, 29 Jul 2020 13:09:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A0B352083B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3CF786E4EC; Wed, 29 Jul 2020 13:09:41 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from fireflyinternet.com (unknown [77.68.26.236]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0C0D56E4EC for ; Wed, 29 Jul 2020 13:09:39 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from build.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 21969151-1500050 for multiple; Wed, 29 Jul 2020 14:09:12 +0100 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Wed, 29 Jul 2020 14:09:12 +0100 Message-Id: <20200729130912.30093-1-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH] drm/i915/display: Check for an LPSP encoder before dereferencing X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Chris Wilson Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Avoid a GPF at <1>[ 20.177320] BUG: kernel NULL pointer dereference, address: 000000000000007c <1>[ 20.177322] #PF: supervisor read access in kernel mode <1>[ 20.177323] #PF: error_code(0x0000) - not-present page <6>[ 20.177324] PGD 0 P4D 0 <4>[ 20.177327] Oops: 0000 [#1] PREEMPT SMP PTI <4>[ 20.177328] CPU: 1 PID: 944 Comm: debugfs_test Not tainted 5.8.0-rc7-CI-CI_DRM_8814+ #1 <4>[ 20.177330] Hardware name: Dell Inc. XPS 13 9360/0823VW, BIOS 2.9.0 07/09/2018 <4>[ 20.177372] RIP: 0010:i915_lpsp_capability_show+0x44/0xc0 [i915] <4>[ 20.177374] Code: 0f b6 81 ca 0d 00 00 3c 0b 74 77 76 19 3c 0c 75 44 83 7e 7c 01 7e 2f 48 c7 c6 d7 b9 47 a0 e8 43 df 06 e1 31 c0 c3 3c 09 72 2b <8b> 46 7c 85 c0 75 e6 8b 82 e4 00 00 00 89 c2 83 e2 fb 83 fa 0a 74 <4>[ 20.177376] RSP: 0018:ffffc90000cebe38 EFLAGS: 00010246 <4>[ 20.177377] RAX: 0000000000000009 RBX: ffff888267fe6a58 RCX: ffff888252d10000 <4>[ 20.177378] RDX: ffff88824a9a4000 RSI: 0000000000000000 RDI: ffff888267fe6a30 <4>[ 20.177379] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001 <4>[ 20.177380] R10: 0000000000000001 R11: 0000000000000000 R12: ffffc90000cebf08 <4>[ 20.177381] R13: 00000000ffffffff R14: 0000000000000001 R15: ffff888267fe6a30 <4>[ 20.177383] FS: 00007f6f9c6b5e40(0000) GS:ffff888276480000(0000) knlGS:0000000000000000 <4>[ 20.177384] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 <4>[ 20.177385] CR2: 000000000000007c CR3: 0000000255f04006 CR4: 00000000003606e0 <4>[ 20.177386] Call Trace: <4>[ 20.177390] seq_read+0xcb/0x420 which is presumably from having no encoder attached at that time. Fixes: 8806211fe7b3 ("drm/i915: Add i915_lpsp_capability debugfs") Signed-off-by: Chris Wilson Cc: Animesh Manna Cc: Anshuman Gupta Cc: Uma Shankar Cc: "Ville Syrjälä" Reviewed-by: Anshuman Gupta --- drivers/gpu/drm/i915/display/intel_display_debugfs.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c index 3644752cc5ec..5a5cfe25085b 100644 --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c @@ -2044,9 +2044,12 @@ DEFINE_SHOW_ATTRIBUTE(i915_hdcp_sink_capability); static int i915_lpsp_capability_show(struct seq_file *m, void *data) { struct drm_connector *connector = m->private; - struct intel_encoder *encoder = - intel_attached_encoder(to_intel_connector(connector)); struct drm_i915_private *i915 = to_i915(connector->dev); + struct intel_encoder *encoder; + + encoder = intel_attached_encoder(to_intel_connector(connector)); + if (!encoder) + return -ENODEV; if (connector->status != connector_status_connected) return -ENODEV;