Commit 2ed8b509 authored by Alexander Gordeev's avatar Alexander Gordeev
Browse files

s390/kasan: fix insecure W+X mapping warning 



Since commit 3b5c3f000c2e ("s390/kasan: move shadow mapping
to decompressor") the decompressor establishes mappings for
the shadow memory and sets initial protection attributes to
RWX. The decompressed kernel resets protection to RW+NX
later on.

In case a shadow memory range is not aligned on page boundary
(e.g. as result of mem= kernel command line parameter use),
the "Checked W+X mappings: FAILED, 1 W+X pages found" warning
hits.

Reported-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Fixes: 557b1970 ("s390/kasan: move shadow mapping to decompressor")
Reviewed-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
parent f471c658

arch/s390/mm/vmem.c

+10 −4
Original line number Diff line number Diff line
@@ -667,7 +667,15 @@ static void __init memblock_region_swap(void *a, void *b, int size) 


#ifdef CONFIG_KASAN

#define __sha(x)	((unsigned long)kasan_mem_to_shadow((void *)x))



static inline int set_memory_kasan(unsigned long start, unsigned long end)

{

	start = PAGE_ALIGN_DOWN(__sha(start));

	end = PAGE_ALIGN(__sha(end));

	return set_memory_rwnx(start, (end - start) >> PAGE_SHIFT);

}

#endif



/*

 * map whole physical memory to virtual memory (identity mapping)

 * we reserve enough space in the vmalloc area for vmemmap to hotplug
@@ -737,10 +745,8 @@ void __init vmem_map_init(void) 
	}



#ifdef CONFIG_KASAN

	for_each_mem_range(i, &base, &end) {

		set_memory_rwnx(__sha(base),

				(__sha(end) - __sha(base)) >> PAGE_SHIFT);

	}

	for_each_mem_range(i, &base, &end)

		set_memory_kasan(base, end);

#endif

	set_memory_rox((unsigned long)_stext,

		       (unsigned long)(_etext - _stext) >> PAGE_SHIFT);