__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. Signed-off-by: Chintan Pandya <cpandya@xxxxxxxxxxxxxx> --- Changes: V1 --> V2 Not touching CONFIG_DEBUG_HIGHMEM. include/linux/highmem.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 7fb31da..9286a46 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -93,7 +93,7 @@ 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); + BUG_ON(idx >= KM_TYPE_NR); #endif return idx; } -- Chintan Pandya QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>