linux-kernel - [PATCH 09/10] mm: Prevent madvise from changing shadow stack

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Date:   Thu,  7 Jun 2018 07:38:06 -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 09/10] mm: Prevent madvise from changing shadow stack

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

diff --git a/mm/madvise.c b/mm/madvise.c
index 4d3c922ea1a1..2a6988badd6b 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -839,6 +839,14 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 	if (vma && start > vma->vm_start)
 		prev = vma;
 
+	/*
+	 * Don't do anything on shadow stack.
+	 */
+	if (vma->vm_flags & VM_SHSTK) {
+		error = -EINVAL;
+		goto out_no_plug;
+	}
+
 	blk_start_plug(&plug);
 	for (;;) {
 		/* Still start < end. */
@@ -876,6 +884,7 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 	}
 out:
 	blk_finish_plug(&plug);
+out_no_plug:
 	if (write)
 		up_write(&current->mm->mmap_sem);
 	else
-- 
2.15.1