From e9c38f9fc2ccd31befe1bb1605b69213483a15b7 Mon Sep 17 00:00:00 2001 From: Stephen Smalley Date: Wed, 8 Jan 2020 11:24:47 -0500 Subject: Documentation,selinux: deprecate setting checkreqprot to 1 Deprecate setting the SELinux checkreqprot tunable to 1 via kernel parameter or /sys/fs/selinux/checkreqprot. Setting it to 0 is left intact for compatibility since Android and some Linux distributions do so for security and treat an inability to set it as a fatal error. Eventually setting it to 0 will become a no-op and the kernel will stop using checkreqprot's value internally altogether. checkreqprot was originally introduced as a compatibility mechanism for legacy userspace and the READ_IMPLIES_EXEC personality flag. However, if set to 1, it weakens security by allowing mappings to be made executable without authorization by policy. The default value for the SECURITY_SELINUX_CHECKREQPROT_VALUE config option was changed from 1 to 0 in commit 2a35d196c160e3 ("selinux: change CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE default") and both Android and Linux distributions began explicitly setting /sys/fs/selinux/checkreqprot to 0 some time ago. Signed-off-by: Stephen Smalley Signed-off-by: Paul Moore --- security/selinux/Kconfig | 3 +++ security/selinux/hooks.c | 5 ++++- security/selinux/selinuxfs.c | 8 ++++++++ 3 files changed, 15 insertions(+), 1 deletion(-) (limited to 'security') diff --git a/security/selinux/Kconfig b/security/selinux/Kconfig index 1014cb0ee956..9e921fc72538 100644 --- a/security/selinux/Kconfig +++ b/security/selinux/Kconfig @@ -88,6 +88,9 @@ config SECURITY_SELINUX_CHECKREQPROT_VALUE 'checkreqprot=' boot parameter. It may also be changed at runtime via /sys/fs/selinux/checkreqprot if authorized by policy. + WARNING: this option is deprecated and will be removed in a future + kernel release. + If you are unsure how to answer this question, answer 0. config SECURITY_SELINUX_SIDTAB_HASH_BITS diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index b33cf155cc48..d7762264f262 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -142,8 +142,11 @@ static int __init checkreqprot_setup(char *str) { unsigned long checkreqprot; - if (!kstrtoul(str, 0, &checkreqprot)) + if (!kstrtoul(str, 0, &checkreqprot)) { selinux_checkreqprot_boot = checkreqprot ? 1 : 0; + if (checkreqprot) + pr_warn("SELinux: checkreqprot set to 1 via kernel parameter. This is deprecated and will be rejected in a future kernel release.\n"); + } return 1; } __setup("checkreqprot=", checkreqprot_setup); diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c index 79c710911a3c..d6566adc73a6 100644 --- a/security/selinux/selinuxfs.c +++ b/security/selinux/selinuxfs.c @@ -668,6 +668,14 @@ static ssize_t sel_write_checkreqprot(struct file *file, const char __user *buf, if (sscanf(page, "%u", &new_value) != 1) goto out; + if (new_value) { + char comm[sizeof(current->comm)]; + + memcpy(comm, current->comm, sizeof(comm)); + pr_warn_once("SELinux: %s (%d) set checkreqprot to 1. This is deprecated and will be rejected in a future kernel release.\n", + comm, current->pid); + } + fsi->state->checkreqprot = new_value ? 1 : 0; length = count; out: -- cgit