selinux: Add helper functions to get and set checkreqprot

checkreqprot data member in selinux_state struct is accessed directly by
SELinux functions to get and set. This could cause unexpected read or
write access to this data member due to compiler optimizations and/or
compiler's reordering of access to this field.

Add helper functions to get and set checkreqprot data member in
selinux_state struct. These helper functions use READ_ONCE and
WRITE_ONCE macros to ensure atomic read or write of memory for
this data member.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Suggested-by: Paul Moore <paul@paul-moore.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 45e9efa9bf5b..4bde570d56a2 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -717,7 +717,8 @@ static ssize_t sel_read_checkreqprot(struct file *filp, char __user *buf,
 	char tmpbuf[TMPBUFLEN];
 	ssize_t length;
 
-	length = scnprintf(tmpbuf, TMPBUFLEN, "%u", fsi->state->checkreqprot);
+	length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
+			   checkreqprot_get(fsi->state));
 	return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
 }
 
@@ -759,7 +760,7 @@ static ssize_t sel_write_checkreqprot(struct file *file, const char __user *buf,
 			     comm, current->pid);
 	}
 
-	fsi->state->checkreqprot = new_value ? 1 : 0;
+	checkreqprot_set(fsi->state, (new_value ? 1 : 0));
 	length = count;
 out:
 	kfree(page);