From f7d83c1cf3c77ae45876792aee5285ae970413ac Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Wed, 16 Aug 2017 13:26:03 -0700
Subject: x86: Implement thread_struct whitelist for hardened usercopy

This whitelists the FPU register state portion of the thread_struct for
copying to userspace, instead of the default entire struct. This is needed
because FPU register state is dynamically sized, so it doesn't bypass the
hardened usercopy checks.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Rik van Riel <riel@redhat.com>
---
 arch/x86/include/asm/processor.h | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'arch/x86/include/asm/processor.h')

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index cc16fa882e3e..2b037b7fe0eb 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -492,6 +492,14 @@ struct thread_struct {
 	 */
 };
 
+/* Whitelist the FPU state from the task_struct for hardened usercopy. */
+static inline void arch_thread_struct_whitelist(unsigned long *offset,
+						unsigned long *size)
+{
+	*offset = offsetof(struct thread_struct, fpu.state);
+	*size = fpu_kernel_xstate_size;
+}
+
 /*
  * Thread-synchronous status.
  *
-- 
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