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-rw-r--r--include/linux/cpumask.h14
1 files changed, 14 insertions, 0 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index b24ac56477b4..4f7a63237471 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -617,6 +617,20 @@ static inline size_t cpumask_size(void)
* ... use 'tmpmask' like a normal struct cpumask * ...
*
* free_cpumask_var(tmpmask);
+ *
+ *
+ * However, one notable exception is there. alloc_cpumask_var() allocates
+ * only nr_cpumask_bits bits (in the other hand, real cpumask_t always has
+ * NR_CPUS bits). Therefore you don't have to dereference cpumask_var_t.
+ *
+ * cpumask_var_t tmpmask;
+ * if (!alloc_cpumask_var(&tmpmask, GFP_KERNEL))
+ * return -ENOMEM;
+ *
+ * var = *tmpmask;
+ *
+ * This code makes NR_CPUS length memcopy and brings to a memory corruption.
+ * cpumask_copy() provide safe copy functionality.
*/
#ifdef CONFIG_CPUMASK_OFFSTACK
typedef struct cpumask *cpumask_var_t;

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