From f86ad57c428b816004f6debae4692736fa16f3a4 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 29 Jul 2020 14:09:12 +0100 Subject: [PATCH] drm/i915/display: Check for an LPSP encoder before dereferencing MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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. Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2175 Fixes: f18a6f441abd ("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 Link: https://patchwork.freedesktop.org/patch/msgid/20200729130912.30093-1-chris@chris-wilson.co.uk Signed-off-by: Rodrigo Vivi (cherry picked from commit a22b1a9bb0d72a58d5b836653f28d97ee8fea1c4) Signed-off-by: Jani Nikula --- 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 3644752cc5ece..5a5cfe25085b4 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; -- 2.39.5