diff mbox

[10/10] mm: Prevent munmap and remap_file_pages of shadow stack

Message ID 20180607143807.3611-11-yu-cheng.yu@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Yu-cheng Yu June 7, 2018, 2:38 p.m. UTC 
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
 mm/mmap.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

Comments

Andy Lutomirski June 7, 2018, 6:50 p.m. UTC | #1 
On Thu, Jun 7, 2018 at 7:41 AM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:

blocking remap_file_pages() seems reasonable.  I'm not sure what's
wrong with munmap().
Yu-cheng Yu June 7, 2018, 8:15 p.m. UTC | #2 
On Thu, 2018-06-07 at 11:50 -0700, Andy Lutomirski wrote:
> On Thu, Jun 7, 2018 at 7:41 AM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:
> 
> blocking remap_file_pages() seems reasonable.  I'm not sure what's
> wrong with munmap().

Yes, maybe we don't need to block munmap().  If the shadow stack is
unmapped, the application gets a fault.  I will remove the patch.
diff mbox

Patch

diff --git a/mm/mmap.c b/mm/mmap.c
index fc41c0543d7f..e7d1fcb7ec58 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2810,6 +2810,16 @@  EXPORT_SYMBOL(vm_munmap);
 
 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
 {
+	struct vm_area_struct *vma;
+
+	/* Do not munmap shadow stack */
+	down_read(&current->mm->mmap_sem);
+	vma = find_vma(current->mm, addr);
+	if (vma && (vma->vm_flags & VM_SHSTK)) {
+		up_read(&current->mm->mmap_sem);
+		return -EINVAL;
+	}
+	up_read(&current->mm->mmap_sem);
 	profile_munmap(addr);
 	return vm_munmap(addr, len);
 }
@@ -2851,6 +2861,9 @@  SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 	if (!vma || !(vma->vm_flags & VM_SHARED))
 		goto out;
 
+	if (vma->vm_flags & VM_SHSTK)
+		goto out;
+
 	if (start < vma->vm_start)
 		goto out;