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monitor-manager-kms: Don't add outputs without modes

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There seems to be a kernel race when one disconnects an external
monitor connected to a DisplayPort via a USB-C adapter. The race
results in a connector being reported as connected, but without any
modes supported.

This had the side effect that we tried to set a preferred mode to
the first listed mode, but as no modes were available, we instead tried
to dereference the first element of a NULL array, causing a
segmentation fault.

Mitigate this by skipping adding output if no supported modes are
advertised and the output doesn't support scaling, while moving the
fallback path for calculating a preferred output mode to after possibly
adding the common modes, to avoid the unvolentary NULL dereference.

https://bugzilla.gnome.org/show_bug.cgi?id=789501
This commit is contained in:
Jonas Ådahl 2017-10-30 18:43:04 +08:00
parent 634f48a1cf
commit 9187314216
1 changed files with 14 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
src/backends/native/meta-monitor-manager-kms.c
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@ -692,7 +692,7 @@ init_crtc (MetaCrtc *crtc,
crtc->driver_notify = (GDestroyNotify) meta_crtc_destroy_notify;
}
static void
static gboolean
init_output (MetaOutput *output,
MetaMonitorManager *manager,
drmModeConnector *connector,
@ -746,9 +746,6 @@ init_output (MetaOutput *output,
output->preferred_mode = output->modes[i];
}
if (!output->preferred_mode)
output->preferred_mode = output->modes[0];
output_kms->connector = connector;
find_connector_properties (manager_kms, output_kms);
@ -759,6 +756,15 @@ init_output (MetaOutput *output,
if (output_kms->has_scaling)
add_common_modes (manager, output);
if (!output->modes)
{
meta_monitor_manager_clear_output (output);
return FALSE;
}
if (!output->preferred_mode)
output->preferred_mode = output->modes[0];
qsort (output->modes, output->n_modes, sizeof (MetaCrtcMode *), compare_modes);
output_kms->n_encoders = connector->count_encoders;
@ -865,6 +871,8 @@ init_output (MetaOutput *output,
output->backlight_min = 0;
output->backlight_max = 0;
output->backlight = -1;
return TRUE;
}
static void
@ -1091,8 +1099,8 @@ init_outputs (MetaMonitorManager *manager,
old_output = find_output_by_id (old_outputs, n_old_outputs,
connector->connector_id);
init_output (output, manager, connector, old_output);
n_actual_outputs++;
if (init_output (output, manager, connector, old_output))
n_actual_outputs++;
}
}