[PATCH] mm: BUG when __kmap_atomic_idx crosses boundary

[Chintan Pandya]

__kmap_atomic_idx >= KM_TYPE_NR or < ZERO is a bug.
Report it even if CONFIG_DEBUG_HIGHMEM is not enabled.
That saves much debugging efforts.

Signed-off-by: Chintan Pandya <cpandya@xxxxxxxxxxxxxx>
---
 include/linux/highmem.h | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 7fb31da..f42cafd 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -93,8 +93,8 @@ static inline int kmap_atomic_idx_push(void)
 
 #ifdef CONFIG_DEBUG_HIGHMEM
 	WARN_ON_ONCE(in_irq() && !irqs_disabled());
-	BUG_ON(idx > KM_TYPE_NR);
 #endif
+	BUG_ON(idx >= KM_TYPE_NR);
 	return idx;
 }
 
@@ -105,13 +105,9 @@ static inline int kmap_atomic_idx(void)
 
 static inline void kmap_atomic_idx_pop(void)
 {
-#ifdef CONFIG_DEBUG_HIGHMEM
 	int idx = __this_cpu_dec_return(__kmap_atomic_idx);
 
 	BUG_ON(idx < 0);
-#else
-	__this_cpu_dec(__kmap_atomic_idx);
-#endif
 }
 
 #endif
-- 
Chintan Pandya

QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation

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