take calculation of final prot in security_mmap_file() into a helper

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/security/security.c b/security/security.c
index 3b11b3b..3efc9b1 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -660,36 +660,46 @@ int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
        return security_ops->file_ioctl(file, cmd, arg);
 }
 
-int security_mmap_file(struct file *file, unsigned long prot,
-                       unsigned long flags)
+static inline unsigned long mmap_prot(struct file *file, unsigned long prot)
 {
-       unsigned long reqprot = prot;
-       int ret;
        /*
-        * Does the application expect PROT_READ to imply PROT_EXEC?
-        *
-        * (the exception is when the underlying filesystem is noexec
-        *  mounted, in which case we dont add PROT_EXEC.)
+        * Does we have PROT_READ and does the application expect
+        * it to imply PROT_EXEC?  If not, nothing to talk about...
         */
-       if (!(reqprot & PROT_READ))
-               goto out;
+       if ((prot & (PROT_READ | PROT_EXEC)) != PROT_READ)
+               return prot;
        if (!(current->personality & READ_IMPLIES_EXEC))
-               goto out;
-       if (!file) {
-               prot |= PROT_EXEC;
-       } else if (!(file->f_path.mnt->mnt_flags & MNT_NOEXEC)) {
+               return prot;
+       /*
+        * if that's an anonymous mapping, let it.
+        */
+       if (!file)
+               return prot | PROT_EXEC;
+       /*
+        * ditto if it's not on noexec mount, except that on !MMU we need
+        * BDI_CAP_EXEC_MMAP (== VM_MAYEXEC) in this case
+        */
+       if (!(file->f_path.mnt->mnt_flags & MNT_NOEXEC)) {
 #ifndef CONFIG_MMU
                unsigned long caps = 0;
                struct address_space *mapping = file->f_mapping;
                if (mapping && mapping->backing_dev_info)
                        caps = mapping->backing_dev_info->capabilities;
                if (!(caps & BDI_CAP_EXEC_MAP))
-                       goto out;
+                       return prot;
 #endif
-               prot |= PROT_EXEC;
+               return prot | PROT_EXEC;
        }
-out:
-       ret = security_ops->mmap_file(file, reqprot, prot, flags);
+       /* anything on noexec mount won't get PROT_EXEC */
+       return prot;
+}
+
+int security_mmap_file(struct file *file, unsigned long prot,
+                       unsigned long flags)
+{
+       int ret;
+       ret = security_ops->mmap_file(file, prot,
+                                       mmap_prot(file, prot), flags);
        if (ret)
                return ret;
        return ima_file_mmap(file, prot);