From 106b4a2a78b2a2f14885604891957b84bba502db Mon Sep 17 00:00:00 2001 From: Adrian Betschart Date: Fri, 11 Sep 2026 17:13:14 +0200 Subject: drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validation 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 Assisted-by: Claude Code:claude-fable-5-1 Signed-off-by: Adrian Betschart Reviewed-by: Fangzhi Zuo Tested-by: Adolfo Rodrigues Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher (cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7) --- security/lockdown/Kconfig | 47 ++++++++++++ security/lockdown/Makefile | 1 + security/lockdown/lockdown.c | 172 +++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 220 insertions(+) create mode 100644 security/lockdown/Kconfig create mode 100644 security/lockdown/Makefile create mode 100644 security/lockdown/lockdown.c (limited to 'security/lockdown') diff --git a/security/lockdown/Kconfig b/security/lockdown/Kconfig new file mode 100644 index 000000000..e84ddf484 --- /dev/null +++ b/security/lockdown/Kconfig @@ -0,0 +1,47 @@ +config SECURITY_LOCKDOWN_LSM + bool "Basic module for enforcing kernel lockdown" + depends on SECURITY + select MODULE_SIG if MODULES + help + Build support for an LSM that enforces a coarse kernel lockdown + behaviour. + +config SECURITY_LOCKDOWN_LSM_EARLY + bool "Enable lockdown LSM early in init" + depends on SECURITY_LOCKDOWN_LSM + help + Enable the lockdown LSM early in boot. This is necessary in order + to ensure that lockdown enforcement can be carried out on kernel + boot parameters that are otherwise parsed before the security + subsystem is fully initialised. If enabled, lockdown will + unconditionally be called before any other LSMs. + +choice + prompt "Kernel default lockdown mode" + default LOCK_DOWN_KERNEL_FORCE_NONE + depends on SECURITY_LOCKDOWN_LSM + help + The kernel can be configured to default to differing levels of + lockdown. + +config LOCK_DOWN_KERNEL_FORCE_NONE + bool "None" + help + No lockdown functionality is enabled by default. Lockdown may be + enabled via the kernel commandline or /sys/kernel/security/lockdown. + +config LOCK_DOWN_KERNEL_FORCE_INTEGRITY + bool "Integrity" + help + The kernel runs in integrity mode by default. Features that allow + the kernel to be modified at runtime are disabled. + +config LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY + bool "Confidentiality" + help + The kernel runs in confidentiality mode by default. Features that + allow the kernel to be modified at runtime or that permit userland + code to read confidential material held inside the kernel are + disabled. + +endchoice diff --git a/security/lockdown/Makefile b/security/lockdown/Makefile new file mode 100644 index 000000000..e3634b901 --- /dev/null +++ b/security/lockdown/Makefile @@ -0,0 +1 @@ +obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown.o diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c new file mode 100644 index 000000000..8d46886d2 --- /dev/null +++ b/security/lockdown/lockdown.c @@ -0,0 +1,172 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Lock down the kernel + * + * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#include +#include +#include +#include + +static enum lockdown_reason kernel_locked_down; + +static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, + LOCKDOWN_INTEGRITY_MAX, + LOCKDOWN_CONFIDENTIALITY_MAX}; + +/* + * Put the kernel into lock-down mode. + */ +static int lock_kernel_down(const char *where, enum lockdown_reason level) +{ + if (kernel_locked_down >= level) + return -EPERM; + + kernel_locked_down = level; + pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", + where); + return 0; +} + +static int __init lockdown_param(char *level) +{ + if (!level) + return -EINVAL; + + if (strcmp(level, "integrity") == 0) + lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); + else if (strcmp(level, "confidentiality") == 0) + lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); + else + return -EINVAL; + + return 0; +} + +early_param("lockdown", lockdown_param); + +/** + * lockdown_is_locked_down - Find out if the kernel is locked down + * @what: Tag to use in notice generated if lockdown is in effect + */ +static int lockdown_is_locked_down(enum lockdown_reason what) +{ + if (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX, + "Invalid lockdown reason")) + return -EPERM; + + if (kernel_locked_down >= what) { + if (lockdown_reasons[what]) + pr_notice_ratelimited("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n", + current->comm, lockdown_reasons[what]); + return -EPERM; + } + + return 0; +} + +static struct security_hook_list lockdown_hooks[] __ro_after_init = { + LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), +}; + +static const struct lsm_id lockdown_lsmid = { + .name = "lockdown", + .id = LSM_ID_LOCKDOWN, +}; + +static int __init lockdown_lsm_init(void) +{ +#if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) + lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); +#elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) + lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); +#endif + security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), + &lockdown_lsmid); + return 0; +} + +static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, + loff_t *ppos) +{ + char temp[80] = ""; + int i, offset = 0; + + for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { + enum lockdown_reason level = lockdown_levels[i]; + + if (lockdown_reasons[level]) { + const char *label = lockdown_reasons[level]; + + if (kernel_locked_down == level) + offset += sprintf(temp+offset, "[%s] ", label); + else + offset += sprintf(temp+offset, "%s ", label); + } + } + + /* Convert the last space to a newline if needed. */ + if (offset > 0) + temp[offset-1] = '\n'; + + return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); +} + +static ssize_t lockdown_write(struct file *file, const char __user *buf, + size_t n, loff_t *ppos) +{ + char *state; + int i, len, err = -EINVAL; + + state = memdup_user_nul(buf, n); + if (IS_ERR(state)) + return PTR_ERR(state); + + len = strlen(state); + if (len && state[len-1] == '\n') { + state[len-1] = '\0'; + len--; + } + + for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { + enum lockdown_reason level = lockdown_levels[i]; + const char *label = lockdown_reasons[level]; + + if (label && !strcmp(state, label)) + err = lock_kernel_down("securityfs", level); + } + + kfree(state); + return err ? err : n; +} + +static const struct file_operations lockdown_ops = { + .read = lockdown_read, + .write = lockdown_write, +}; + +static int __init lockdown_secfs_init(void) +{ + struct dentry *dentry; + + dentry = securityfs_create_file("lockdown", 0644, NULL, NULL, + &lockdown_ops); + return PTR_ERR_OR_ZERO(dentry); +} + +#ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY +DEFINE_EARLY_LSM(lockdown) = { +#else +DEFINE_LSM(lockdown) = { +#endif + .id = &lockdown_lsmid, + .init = lockdown_lsm_init, + .initcall_core = lockdown_secfs_init, +}; -- cgit v1.3.1