drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validationgrafted

amdgpu_dm_create_validate_stream_for_sink() walks encoding_order[] and
uses the first encoding that validates. YCbCr 4:4:4 is listed before
RGB, so an HDMI sink that advertises 4:4:4 gets YCbCr 4:4:4 whenever the
"color format" property is left at AUTO, even though RGB fits the same
link.

That contradicts the documented AUTO behaviour for HDMI in enum
drm_connector_color_format (RGB, falling back to YCbCr 4:2:0 only when
the bandwidth is not available or the mode is 4:2:0-only), which the
amdgpu implementation of the property also describes. It also leaves
the "Broadcast RGB" property without effect on such sinks, since the
quantization range it selects only applies to RGB output.

Try RGB first. The mask still holds every encoding the sink supports,
so a mode that cannot carry RGB falls back exactly as before.

For reference, v7.2 picked RGB here unless YCbCr 4:4:4 was forced
through debugfs, while earlier kernels picked YCbCr 4:4:4 for any HDMI
sink that advertised it.

Fixes: 0b0ff65d3ca1 ("drm/amd/display: Refactor stream validation")
Suggested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Assisted-by: Claude Code:claude-fable-5-1
Signed-off-by: Adrian Betschart <adrian.betschart@cinemaone.ch>
Reviewed-by: Fangzhi Zuo <jerry.zuo@amd.com>
Tested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7)

1 files changed, 222 insertions, 0 deletions

diff --git a/security/apparmor/path.c b/security/apparmor/path.c
new file mode 100644
index 000000000..2494e8101
--- /dev/null
+++ b/security/apparmor/path.c
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor function for pathnames
+ *
+ * Copyright (C) 1998-2008 Novell/SUSE
+ * Copyright 2009-2010 Canonical Ltd.
+ */
+
+#include <linux/magic.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/nsproxy.h>
+#include <linux/path.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/fs_struct.h>
+
+#include "include/apparmor.h"
+#include "include/path.h"
+#include "include/policy.h"
+
+/* modified from dcache.c */
+static int prepend(char **buffer, int buflen, const char *str, int namelen)
+{
+	buflen -= namelen;
+	if (buflen < 0)
+		return -ENAMETOOLONG;
+	*buffer -= namelen;
+	memcpy(*buffer, str, namelen);
+	return 0;
+}
+
+#define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
+
+/* If the path is not connected to the expected root,
+ * check if it is a sysctl and handle specially else remove any
+ * leading / that __d_path may have returned.
+ * Unless
+ *     specifically directed to connect the path,
+ * OR
+ *     if in a chroot and doing chroot relative paths and the path
+ *     resolves to the namespace root (would be connected outside
+ *     of chroot) and specifically directed to connect paths to
+ *     namespace root.
+ */
+static int disconnect(const struct path *path, char *buf, char **name,
+		      int flags, const char *disconnected)
+{
+	int error = 0;
+
+	if (!(flags & PATH_CONNECT_PATH) &&
+	    !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
+	      our_mnt(path->mnt))) {
+		/* disconnected path, don't return pathname starting
+		 * with '/'
+		 */
+		error = -EACCES;
+		if (**name == '/')
+			*name = *name + 1;
+	} else {
+		if (**name != '/')
+			/* CONNECT_PATH with missing root */
+			error = prepend(name, *name - buf, "/", 1);
+		if (!error && disconnected)
+			error = prepend(name, *name - buf, disconnected,
+					strlen(disconnected));
+	}
+
+	return error;
+}
+
+/**
+ * d_namespace_path - lookup a name associated with a given path
+ * @path: path to lookup  (NOT NULL)
+ * @buf:  buffer to store path to  (NOT NULL)
+ * @name: Returns - pointer for start of path name with in @buf (NOT NULL)
+ * @flags: flags controlling path lookup
+ * @disconnected: string to prefix to disconnected paths
+ *
+ * Handle path name lookup.
+ *
+ * Returns: %0 else error code if path lookup fails
+ *          When no error the path name is returned in @name which points to
+ *          a position in @buf
+ */
+static int d_namespace_path(const struct path *path, char *buf, char **name,
+			    int flags, const char *disconnected)
+{
+	char *res;
+	int error = 0;
+	int connected = 1;
+	int isdir = (flags & PATH_IS_DIR) ? 1 : 0;
+	int buflen = aa_g_path_max - isdir;
+
+	if (path->mnt->mnt_flags & MNT_INTERNAL) {
+		/* it's not mounted anywhere */
+		res = dentry_path(path->dentry, buf, buflen);
+		*name = res;
+		if (IS_ERR(res)) {
+			*name = buf;
+			return PTR_ERR(res);
+		}
+		if (path->dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
+		    strncmp(*name, "/sys/", 5) == 0) {
+			/* TODO: convert over to using a per namespace
+			 * control instead of hard coded /proc
+			 */
+			error = prepend(name, *name - buf, "/proc", 5);
+			goto out;
+		} else
+			error = disconnect(path, buf, name, flags,
+					   disconnected);
+		goto out;
+	}
+
+	/* resolve paths relative to chroot?*/
+	if (flags & PATH_CHROOT_REL) {
+		struct path root;
+		get_fs_root(current->fs, &root);
+		res = __d_path(path, &root, buf, buflen);
+		path_put(&root);
+	} else {
+		res = d_absolute_path(path, buf, buflen);
+		if (!our_mnt(path->mnt))
+			connected = 0;
+	}
+
+	/* handle error conditions - and still allow a partial path to
+	 * be returned.
+	 */
+	if (IS_ERR_OR_NULL(res)) {
+		if (PTR_ERR(res) == -ENAMETOOLONG) {
+			error = -ENAMETOOLONG;
+			*name = buf;
+			goto out;
+		}
+		connected = 0;
+		res = dentry_path_raw(path->dentry, buf, buflen);
+		if (IS_ERR(res)) {
+			error = PTR_ERR(res);
+			*name = buf;
+			goto out;
+		}
+	} else if (!our_mnt(path->mnt))
+		connected = 0;
+
+	*name = res;
+
+	if (!connected)
+		error = disconnect(path, buf, name, flags, disconnected);
+
+	/* Handle two cases:
+	 * 1. A deleted dentry && profile is not allowing mediation of deleted
+	 * 2. On some filesystems, newly allocated dentries appear to the
+	 *    security_path hooks as a deleted dentry except without an inode
+	 *    allocated.
+	 */
+	if (d_unlinked(path->dentry) && d_is_positive(path->dentry) &&
+	    !(flags & (PATH_MEDIATE_DELETED | PATH_DELEGATE_DELETED))) {
+			error = -ENOENT;
+			goto out;
+	}
+
+out:
+	/* Append "/" to directory paths and reterminate string, except for
+	 * root "/" which already ends in a slash.
+	 */
+	if (!error && isdir) {
+		bool is_root = (*name)[0] == '/' && (*name)[1] == '\0';
+
+		if (!is_root) {
+			buf[aa_g_path_max - 2] = '/';
+			buf[aa_g_path_max - 1] = '\0';
+		}
+	}
+
+	return error;
+}
+
+/**
+ * aa_path_name - get the pathname to a buffer ensure dir / is appended
+ * @path: path the file  (NOT NULL)
+ * @flags: flags controlling path name generation
+ * @buffer: buffer to put name in (NOT NULL)
+ * @name: Returns - the generated path name if !error (NOT NULL)
+ * @info: Returns - information on why the path lookup failed (MAYBE NULL)
+ * @disconnected: string to prepend to disconnected paths
+ *
+ * @name is a pointer to the beginning of the pathname (which usually differs
+ * from the beginning of the buffer), or NULL.  If there is an error @name
+ * may contain a partial or invalid name that can be used for audit purposes,
+ * but it can not be used for mediation.
+ *
+ * We need PATH_IS_DIR to indicate whether the file is a directory or not
+ * because the file may not yet exist, and so we cannot check the inode's
+ * file type.
+ *
+ * Returns: %0 else error code if could retrieve name
+ */
+int aa_path_name(const struct path *path, int flags, char *buffer,
+		 const char **name, const char **info, const char *disconnected)
+{
+	char *str = NULL;
+	int error = d_namespace_path(path, buffer, &str, flags, disconnected);
+
+	if (info && error) {
+		if (error == -ENOENT)
+			*info = "Failed name lookup - deleted entry";
+		else if (error == -EACCES)
+			*info = "Failed name lookup - disconnected path";
+		else if (error == -ENAMETOOLONG)
+			*info = "Failed name lookup - name too long";
+		else
+			*info = "Failed name lookup";
+	}
+
+	*name = str;
+
+	return error;
+}