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

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

1 files changed, 28 insertions, 18 deletions

diff --git a/security/security.c b/security/security.c
index 3b11b3b72fe2..3efc9b12aef4 100644
--- 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);