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drm/edid: Don't accept any old garbage as a display descriptor

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Currently we assume any 18 byte descriptor to be a display descritor
if only the tag byte matches the expected value. But for detailed
timing descriptors that same byte is just the lower 8 bits of
hblank, and as such can match any display descriptor tag. To
properly validate that the 18 byte descriptor is in fact a
display descriptor we must also examine bytes 0-2 (just byte 1
should actually suffice but the spec does say that bytes 0 and
2 must also always be zero for display descriptors so we check
those too).

Unlike Allen's original proposed patch to just fix is_rb() we
roll this out across the board to fix everything.

Cc: Allen Chen <allen.chen@ite.com.tw>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200124200231.10517-2-ville.syrjala@linux.intel.com
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
This commit is contained in:
Ville Syrjälä 2020-01-24 22:02:25 +02:00
parent 7304b9810a
commit a7a131ac18
1 changed files with 41 additions and 24 deletions
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65
drivers/gpu/drm/drm_edid.c
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@ -2212,6 +2212,12 @@ struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
}
EXPORT_SYMBOL(drm_mode_find_dmt);
static bool is_display_descriptor(const u8 d[18], u8 tag)
{
return d[0] == 0x00 && d[1] == 0x00 &&
d[2] == 0x00 && d[3] == tag;
}
typedef void detailed_cb(struct detailed_timing *timing, void *closure);
static void
@ -2273,9 +2279,12 @@ static void
is_rb(struct detailed_timing *t, void *data)
{
u8 *r = (u8 *)t;
if (r[3] == EDID_DETAIL_MONITOR_RANGE)
if (r[15] & 0x10)
*(bool *)data = true;
if (!is_display_descriptor(r, EDID_DETAIL_MONITOR_RANGE))
return;
if (r[15] & 0x10)
*(bool *)data = true;
}
/* EDID 1.4 defines this explicitly. For EDID 1.3, we guess, badly. */
@ -2295,7 +2304,11 @@ static void
find_gtf2(struct detailed_timing *t, void *data)
{
u8 *r = (u8 *)t;
if (r[3] == EDID_DETAIL_MONITOR_RANGE && r[10] == 0x02)
if (!is_display_descriptor(r, EDID_DETAIL_MONITOR_RANGE))
return;
if (r[10] == 0x02)
*(u8 **)data = r;
}
@ -2834,7 +2847,7 @@ do_inferred_modes(struct detailed_timing *timing, void *c)
struct detailed_non_pixel *data = &timing->data.other_data;
struct detailed_data_monitor_range *range = &data->data.range;
if (data->type != EDID_DETAIL_MONITOR_RANGE)
if (!is_display_descriptor((const u8 *)timing, EDID_DETAIL_MONITOR_RANGE))
return;
closure->modes += drm_dmt_modes_for_range(closure->connector,
@ -2913,10 +2926,11 @@ static void
do_established_modes(struct detailed_timing *timing, void *c)
{
struct detailed_mode_closure *closure = c;
struct detailed_non_pixel *data = &timing->data.other_data;
if (data->type == EDID_DETAIL_EST_TIMINGS)
closure->modes += drm_est3_modes(closure->connector, timing);
if (!is_display_descriptor((const u8 *)timing, EDID_DETAIL_EST_TIMINGS))
return;
closure->modes += drm_est3_modes(closure->connector, timing);
}
/**
@ -2965,19 +2979,19 @@ do_standard_modes(struct detailed_timing *timing, void *c)
struct detailed_non_pixel *data = &timing->data.other_data;
struct drm_connector *connector = closure->connector;
struct edid *edid = closure->edid;
int i;
if (data->type == EDID_DETAIL_STD_MODES) {
int i;
for (i = 0; i < 6; i++) {
struct std_timing *std;
struct drm_display_mode *newmode;
if (!is_display_descriptor((const u8 *)timing, EDID_DETAIL_STD_MODES))
return;
std = &data->data.timings[i];
newmode = drm_mode_std(connector, edid, std);
if (newmode) {
drm_mode_probed_add(connector, newmode);
closure->modes++;
}
for (i = 0; i < 6; i++) {
struct std_timing *std = &data->data.timings[i];
struct drm_display_mode *newmode;
newmode = drm_mode_std(connector, edid, std);
if (newmode) {
drm_mode_probed_add(connector, newmode);
closure->modes++;
}
}
}
@ -3072,10 +3086,11 @@ static void
do_cvt_mode(struct detailed_timing *timing, void *c)
{
struct detailed_mode_closure *closure = c;
struct detailed_non_pixel *data = &timing->data.other_data;
if (data->type == EDID_DETAIL_CVT_3BYTE)
closure->modes += drm_cvt_modes(closure->connector, timing);
if (!is_display_descriptor((const u8 *)timing, EDID_DETAIL_CVT_3BYTE))
return;
closure->modes += drm_cvt_modes(closure->connector, timing);
}
static int
@ -4301,8 +4316,10 @@ drm_parse_hdmi_vsdb_audio(struct drm_connector *connector, const u8 *db)
static void
monitor_name(struct detailed_timing *t, void *data)
{
if (t->data.other_data.type == EDID_DETAIL_MONITOR_NAME)
*(u8 **)data = t->data.other_data.data.str.str;
if (!is_display_descriptor((const u8 *)t, EDID_DETAIL_MONITOR_NAME))
return;
*(u8 **)data = t->data.other_data.data.str.str;
}
static int get_monitor_name(struct edid *edid, char name[13])