[PATCH] NX: fix read_implies_exec() related noexec-fs breakage

mmap() done from older !pt_gnu_stack binaries on noexec mounted filesystems
could fail due to the extra PROT_EXEC bit.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/mmap.c

@@ -773,13 +773,6 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
 	int accountable = 1;
 	unsigned long charged = 0;
 
-	/*
-	 * Does the application expect PROT_READ to imply PROT_EXEC:
-	 */
-	if (unlikely((prot & PROT_READ) &&
-			(current->personality & READ_IMPLIES_EXEC)))
-		prot |= PROT_EXEC;
-
 	if (file) {
 		if (is_file_hugepages(file))
 			accountable = 0;
@@ -791,6 +784,15 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
 		    (file->f_vfsmnt->mnt_flags & MNT_NOEXEC))
 			return -EPERM;
 	}
+	/*
+	 * 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.)
+	 */
+	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
+		if (!(file && (file->f_vfsmnt->mnt_flags & MNT_NOEXEC)))
+			prot |= PROT_EXEC;
 
 	if (!len)
 		return addr;