Commit 1d352bfd authored Aug 06, 2014 by Chintan Pandya Committed by Linus Torvalds Aug 06, 2014

mm: BUG when __kmap_atomic_idx equals KM_TYPE_NR



__kmap_atomic_idx is per_cpu variable.  Each CPU can use KM_TYPE_NR
entries from FIXMAP i.e.  from 0 to KM_TYPE_NR - 1.  Allowing
__kmap_atomic_idx to over- shoot to KM_TYPE_NR can mess up with next
CPU's 0th entry which is a bug.  Hence BUG_ON if __kmap_atomic_idx >=
KM_TYPE_NR.

Fix the off-by-on in this test.

Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 61e02c74

include/linux/highmem.h

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -93,7 +93,7 @@ static inline int kmap_atomic_idx_push(void)

	#ifdef CONFIG_DEBUG_HIGHMEM		#ifdef CONFIG_DEBUG_HIGHMEM
	WARN_ON_ONCE(in_irq() && !irqs_disabled());		WARN_ON_ONCE(in_irq() && !irqs_disabled());
	BUG_ON(idx > KM_TYPE_NR);		BUG_ON(idx >= KM_TYPE_NR);
	#endif		#endif
	return idx;		return idx;
	}		}