linux-kernel - [PATCH 10/10] mm: Prevent munmap and remap_file

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Date:   Thu,  7 Jun 2018 07:38:07 -0700
From:   Yu-cheng Yu <yu-cheng.yu@...el.com>
To:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, linux-arch@...r.kernel.org, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        Jonathan Corbet <corbet@....net>,
        Oleg Nesterov <oleg@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        Mike Kravetz <mike.kravetz@...cle.com>
Cc:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [PATCH 10/10] mm: Prevent munmap and remap_file_pages of shadow stack

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
---
 mm/mmap.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

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;
 
-- 
2.15.1