um: Mark stub pages mapping with VM_PFNMAP

Ensure that a process cannot destroy his stub pages with
using MADV_DONTNEED and friends.

Reported-by: toralf.foerster@gmx.de
Signed-off-by: Richard Weinberger <richard@nod.at>

diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index ff03067a3b1496acf3725019b31ed17020ea5233..007d5503f49b79bfccbfbe842bbe630fbc625ac1 100644 (file)
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -123,7 +123,7 @@ void uml_setup_stubs(struct mm_struct *mm)
        /* dup_mmap already holds mmap_sem */
        err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
                                      VM_READ | VM_MAYREAD | VM_EXEC |
-                                     VM_MAYEXEC | VM_DONTCOPY,
+                                     VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP,
                                      mm->context.stub_pages);
        if (err) {
                printk(KERN_ERR "install_special_mapping returned %d\n", err);