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    mm: fix find_vma_prev · 83cd904d
    Mikulas Patocka 提交于
    Commit 6bd4837d ("mm: simplify find_vma_prev()") broke memory
    management on PA-RISC.
    
    After application of the patch, programs that allocate big arrays on the
    stack crash with segfault, for example, this will crash if compiled
    without optimization:
    
      int main()
      {
    	char array[200000];
    	array[199999] = 0;
    	return 0;
      }
    
    The reason is that PA-RISC has up-growing stack and the stack is usually
    the last memory area.  In the above example, a page fault happens above
    the stack.
    
    Previously, if we passed too high address to find_vma_prev, it returned
    NULL and stored the last VMA in *pprev.  After "simplify find_vma_prev"
    change, it stores NULL in *pprev.  Consequently, the stack area is not
    found and it is not expanded, as it used to be before the change.
    
    This patch restores the old behavior and makes it return the last VMA in
    *pprev if the requested address is higher than address of any other VMA.
    Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
    Acked-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    83cd904d
mmap.c 69.8 KB