Commit ab76f7b4 authored Oct 01, 2015 by Stephen Smalley Committed by Ingo Molnar Oct 02, 2015

x86/mm: Set NX on gap between __ex_table and rodata



Unused space between the end of __ex_table and the start of
rodata can be left W+x in the kernel page tables.  Extend the
setting of the NX bit to cover this gap by starting from
text_end rather than rodata_start.

  Before:
  ---[ High Kernel Mapping ]---
  0xffffffff80000000-0xffffffff81000000          16M                               pmd
  0xffffffff81000000-0xffffffff81600000           6M     ro         PSE     GLB x  pmd
  0xffffffff81600000-0xffffffff81754000        1360K     ro                 GLB x  pte
  0xffffffff81754000-0xffffffff81800000         688K     RW                 GLB x  pte
  0xffffffff81800000-0xffffffff81a00000           2M     ro         PSE     GLB NX pmd
  0xffffffff81a00000-0xffffffff81b3b000        1260K     ro                 GLB NX pte
  0xffffffff81b3b000-0xffffffff82000000        4884K     RW                 GLB NX pte
  0xffffffff82000000-0xffffffff82200000           2M     RW         PSE     GLB NX pmd
  0xffffffff82200000-0xffffffffa0000000         478M                               pmd

  After:
  ---[ High Kernel Mapping ]---
  0xffffffff80000000-0xffffffff81000000          16M                               pmd
  0xffffffff81000000-0xffffffff81600000           6M     ro         PSE     GLB x  pmd
  0xffffffff81600000-0xffffffff81754000        1360K     ro                 GLB x  pte
  0xffffffff81754000-0xffffffff81800000         688K     RW                 GLB NX pte
  0xffffffff81800000-0xffffffff81a00000           2M     ro         PSE     GLB NX pmd
  0xffffffff81a00000-0xffffffff81b3b000        1260K     ro                 GLB NX pte
  0xffffffff81b3b000-0xffffffff82000000        4884K     RW                 GLB NX pte
  0xffffffff82000000-0xffffffff82200000           2M     RW         PSE     GLB NX pmd
  0xffffffff82200000-0xffffffffa0000000         478M                               pmd

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: <stable@vger.kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1443704662-3138-1-git-send-email-sds@tycho.nsa.gov


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent e3c41e37

arch/x86/mm/init_64.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -1132,7 +1132,7 @@ void mark_rodata_ro(void)
	* has been zapped already via cleanup_highmem().		* has been zapped already via cleanup_highmem().
	*/		*/
	all_end = roundup((unsigned long)_brk_end, PMD_SIZE);		all_end = roundup((unsigned long)_brk_end, PMD_SIZE);
	set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT);		set_memory_nx(text_end, (all_end - text_end) >> PAGE_SHIFT);

	rodata_test();		rodata_test();

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