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Documentation,selinux: deprecate setting checkreqprot to 1

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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 2a35d196c1 ("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@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Stephen Smalley
2020-01-08 11:24:47 -05:00
committed by Paul Moore
parent 4b36cb773a
commit e9c38f9fc2
6 changed files with 40 additions and 1 deletions
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8
security/selinux/selinuxfs.c
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@@ -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: