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 <ch...@chris-wilson.co.uk>
Cc: Animesh Manna <animesh.ma...@intel.com>
Cc: Anshuman Gupta <anshuman.gu...@intel.com>
Cc: Uma Shankar <uma.shan...@intel.com>
Cc: "Ville Syrjälä" <ville.syrj...@linux.intel.com>
---
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;
--
2.20.1
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