SELinux: call cap_file_mmap in selinux_file_mmap

Currently SELinux does not check CAP_SYS_RAWIO in the file_mmap hook.  This
means there is no DAC check on the ability to mmap low addresses in the
memory space.  This function adds the DAC check for CAP_SYS_RAWIO while
maintaining the selinux check on mmap_zero.  This means that processes
which need to mmap low memory will need CAP_SYS_RAWIO and mmap_zero but will
NOT need the SELinux sys_rawio capability.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 1e8cfc4..e6d1432 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3030,9 +3030,21 @@ static int selinux_file_mmap(struct file *file, unsigned long reqprot,
        int rc = 0;
        u32 sid = current_sid();
 
-       if (addr < mmap_min_addr)
+       /*
+        * notice that we are intentionally putting the SELinux check before
+        * the secondary cap_file_mmap check.  This is such a likely attempt
+        * at bad behaviour/exploit that we always want to get the AVC, even
+        * if DAC would have also denied the operation.
+        */
+       if (addr < mmap_min_addr) {
                rc = avc_has_perm(sid, sid, SECCLASS_MEMPROTECT,
                                  MEMPROTECT__MMAP_ZERO, NULL);
+               if (rc)
+                       return rc;
+       }
+
+       /* do DAC check on address space usage */
+       rc = cap_file_mmap(file, reqprot, prot, flags, addr, addr_only);
        if (rc || addr_only)
                return rc;