linux-kernel - [PATCH 07/10] mm: Prevent mprotect from changing shadow stack

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Date:   Thu,  7 Jun 2018 07:38:04 -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 07/10] mm: Prevent mprotect from changing shadow stack

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
---
 mm/mprotect.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 625608bc8962..128dcb880c12 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -446,6 +446,15 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 	error = -ENOMEM;
 	if (!vma)
 		goto out;
+
+	/*
+	 * Do not allow changing shadow stack memory.
+	 */
+	if (vma->vm_flags & VM_SHSTK) {
+		error = -EINVAL;
+		goto out;
+	}
+
 	prev = vma->vm_prev;
 	if (unlikely(grows & PROT_GROWSDOWN)) {
 		if (vma->vm_start >= end)
-- 
2.15.1