linux-kernel - [PATCH 08/10] mm: Prevent mremap of shadow stack

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Date:   Thu,  7 Jun 2018 07:38:05 -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 08/10] mm: Prevent mremap of shadow stack

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
---
 mm/mremap.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/mremap.c b/mm/mremap.c
index 049470aa1e3e..70f20edb248e 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -525,7 +525,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 		unsigned long, new_addr)
 {
 	struct mm_struct *mm = current->mm;
-	struct vm_area_struct *vma;
+	struct vm_area_struct *vma = find_vma(mm, addr);
 	unsigned long ret = -EINVAL;
 	unsigned long charged = 0;
 	bool locked = false;
@@ -533,6 +533,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 	LIST_HEAD(uf_unmap_early);
 	LIST_HEAD(uf_unmap);
 
+	if (vma->vm_flags & VM_SHSTK)
+		return ret;
+
 	if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 		return ret;
 
-- 
2.15.1