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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: Vasily Gorbik <gor@linux.ibm.com>
Fixes: 557b19709d ("s390/kasan: move shadow mapping to decompressor")
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Alexander Gordeev 2023-05-26 14:30:29 +02:00
parent f471c6585c
commit 2ed8b50975
1 changed files with 10 additions and 4 deletions
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14
arch/s390/mm/vmem.c
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@ -667,7 +667,15 @@ static void __init memblock_region_swap(void *a, void *b, int size)
#ifdef CONFIG_KASAN #ifdef CONFIG_KASAN
#define __sha(x) ((unsigned long)kasan_mem_to_shadow((void *)x)) #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 #endif
/* /*
* map whole physical memory to virtual memory (identity mapping) * map whole physical memory to virtual memory (identity mapping)
* we reserve enough space in the vmalloc area for vmemmap to hotplug * 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 #ifdef CONFIG_KASAN
for_each_mem_range(i, &base, &end) { for_each_mem_range(i, &base, &end)
set_memory_rwnx(__sha(base), set_memory_kasan(base, end);
(__sha(end) - __sha(base)) >> PAGE_SHIFT);
}
#endif #endif
set_memory_rox((unsigned long)_stext, set_memory_rox((unsigned long)_stext,
(unsigned long)(_etext - _stext) >> PAGE_SHIFT); (unsigned long)(_etext - _stext) >> PAGE_SHIFT);