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Commit 656dad31 authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds
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[PATCH] highmem: catch illegal nesting 



Catch illegally nested kmap_atomic()s even if the page that is mapped by
the 'inner' instance is from lowmem.

This avoids spuriously zapped kmap-atomic ptes and turns hard to find
crashes into clear asserts at the bug site.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3e4fdaf8

arch/i386/mm/highmem.c

+4 −3
Original line number Original line Diff line number Diff line
@@ -33,13 +33,14 @@ void *kmap_atomic(struct page *page, enum km_type type) 




	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */

	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */

	pagefault_disable();

	pagefault_disable();



	idx = type + KM_TYPE_NR*smp_processor_id();

	BUG_ON(!pte_none(*(kmap_pte-idx)));



	if (!PageHighMem(page))

	if (!PageHighMem(page))

		return page_address(page);

		return page_address(page);





	idx = type + KM_TYPE_NR*smp_processor_id();

	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);

	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);

	if (!pte_none(*(kmap_pte-idx)))

		BUG();

	set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));

	set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));





	return (void*) vaddr;

	return (void*) vaddr;