From 91fef5b83ce6c19bfe0c695b597b01f3ca074c1c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Fri, 13 Mar 2020 18:20:53 +0200
Subject: drm/edid: Clarify validate_displayid()
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Git-commit: bd1f64df3135ea50827a36dfa3b15d81249e1a37
Patch-mainline: v5.8-rc1
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322
Throw out the magic '5' from validate_displayid() and replace with
the actual thing we mean sizeof(header)+checksum. Also rewrite the
checksum loop to be less hard to parse for mere mortals.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200313162054.16009-9-ville.syrjala@linux.intel.com
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/drm_edid.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 9063cbe6a665..fa7b36be0b96 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -5098,7 +5098,7 @@ u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edi
static int validate_displayid(u8 *displayid, int length, int idx)
{
- int i;
+ int i, dispid_length;
u8 csum = 0;
struct displayid_hdr *base;
@@ -5107,15 +5107,18 @@ static int validate_displayid(u8 *displayid, int length, int idx)
DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n",
base->rev, base->bytes, base->prod_id, base->ext_count);
- if (base->bytes + 5 > length - idx)
+ /* +1 for DispID checksum */
+ dispid_length = sizeof(*base) + base->bytes + 1;
+ if (dispid_length > length - idx)
return -EINVAL;
- for (i = idx; i <= base->bytes + 5; i++) {
- csum += displayid[i];
- }
+
+ for (i = 0; i < dispid_length; i++)
+ csum += displayid[idx + i];
if (csum) {
DRM_NOTE("DisplayID checksum invalid, remainder is %d\n", csum);
return -EINVAL;
}
+
return 0;
}
--
2.28.0