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 <sds@xxxxxxxxxxxxx>
---
RFC-only, not yet tested.
Documentation/admin-guide/kernel-parameters.txt | 1 +
security/selinux/Kconfig | 3 +++
security/selinux/hooks.c | 4 ++++
security/selinux/selinuxfs.c | 6 ++++++
4 files changed, 14 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index eed51293d6cf..c894ddfa1393 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -512,6 +512,7 @@
Default value is set via a kernel config option.
Value can be changed at runtime via
/sys/fs/selinux/checkreqprot.
+ Setting checkreqprot to 1 is deprecated.
cio_ignore= [S390]
See Documentation/s390/common_io.rst for details.
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 63a6e36abe9f..11d47bb7d40a 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -7149,7 +7149,11 @@ static __init int selinux_init(void)
memset(&selinux_state, 0, sizeof(selinux_state));
enforcing_set(&selinux_state, selinux_enforcing_boot);
+
selinux_state.checkreqprot = selinux_checkreqprot_boot;
+ if (selinux_state.checkreqprot)
+ pr_warn("SELinux: checkreqprot set to 1 via kernel parameter. This is deprecated.\n");
+
selinux_ss_init(&selinux_state.ss);
selinux_avc_init(&selinux_state.avc);
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 79c710911a3c..c6c136eee371 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -668,6 +668,12 @@ 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.\n", comm, current->pid);
+ }
+
fsi->state->checkreqprot = new_value ? 1 : 0;
length = count;
out:
--
2.24.1
