linux-kernel - [PATCH] x86/mm: Fix ELF_ET_DYN

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Date:   Tue,  7 Nov 2017 13:38:04 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>, Ingo Molnar <mingo@...e.hu>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nicholas Piggin <npiggin@...il.com>
Subject: [PATCH] x86/mm: Fix ELF_ET_DYN_BASE for 5-level paging

On machines with 5-level paging we don't want to allocate mapping above
47-bit unless user explicitly asked for it. See b569bab78d8d ("x86/mm:
Prepare to expose larger address space to userspace") for details.

c715b72c1ba4 ("mm: revert x86_64 and arm64 ELF_ET_DYN_BASE base
changes") broke the behaviour. After the commit elf binary and heap got
mapped above 47-bits.

Let's fix this.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Fixes: c715b72c1ba4 ("mm: revert x86_64 and arm64 ELF_ET_DYN_BASE base changes")
Cc: Kees Cook <keescook@...omium.org>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Nicholas Piggin <npiggin@...il.com>
---
 arch/x86/include/asm/elf.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index c1a125e47ff3..3a091cea36c5 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -253,7 +253,7 @@ extern int force_personality32;
  * space open for things that want to use the area for 32-bit pointers.
  */
 #define ELF_ET_DYN_BASE		(mmap_is_ia32() ? 0x000400000UL : \
-						  (TASK_SIZE / 3 * 2))
+						  (DEFAULT_MAP_WINDOW / 3 * 2))
 
 /* This yields a mask that user programs can use to figure out what
    instruction set this CPU supports.  This could be done in user space,
-- 
2.14.2