x86/mm: Fix ELF_ET_DYN_BASE for 5-level paging

kiryl · KAGA-KOKO · commit be739f4b5dde · 2017-11-09T18:20:20.000+01:00
On machines with 5-level paging we don't want to allocate mapping above 47-bit unless user explicitly asked for it. See b569bab ("x86/mm: Prepare to expose larger address space to userspace") for details. c715b72 ("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. Use DEFAULT_MAP_WINDOW instead of TASK_SIZE to determine ELF_ET_DYN_BASE so it's forced to be below 47-bits unconditionally. Fixes: c715b72 ("mm: revert x86_64 and arm64 ELF_ET_DYN_BASE base changes") Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Kees Cook <keescook@chromium.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: linux-mm@kvack.org Cc: Andrew Morton <akpm@linux-foundation.org> Link: https://lkml.kernel.org/r/20171107103804.47341-1-kirill.shutemov@linux.intel.com
diff --git 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,
