mm: (k)vrealloc: document concurrency restrictions

Document that concurrent calls to vrealloc() with itself or vfree() for the same memory allocation are not permitted, since it leads to undefined behavior.

Consequently, the same applies for kvrealloc(), hence also document it for kvrealloc().

Suggested-by Christoph Hellwig <[email protected]>

Suggested-by Uladzislau Rezki <[email protected]>

Signed-off-by Danilo Krummrich <[email protected]>

---
 mm/util.c    | 3 +++
 mm/vmalloc.c | 3 +++
 2 files changed, 6 insertions(+)

mm/util.c +3 -0

index 0ff5898cc6de..29ae93f6344f 100644
@@ -732,6 +732,9 @@ EXPORT_SYMBOL(kvfree_sensitive);
  * If @p is %NULL, kvrealloc() behaves exactly like kvmalloc(). If @size is 0
  * and @p is not a %NULL pointer, the object pointed to is freed.
  *
+ * This function must not be called concurrently with itself or kvfree() for the
+ * same memory allocation.
+ *
  * Return: pointer to the allocated memory or %NULL in case of error
  */
 void *kvrealloc_noprof(const void *p, size_t size, gfp_t flags)

mm/vmalloc.c +3 -0

index caf032f0bd69..2a6d4ce57b73 100644
@@ -4049,6 +4049,9 @@ EXPORT_SYMBOL(vzalloc_node_noprof);
  * If @p is %NULL, vrealloc() behaves exactly like vmalloc(). If @size is 0 and
  * @p is not a %NULL pointer, the object pointed to is freed.
  *
+ * This function must not be called concurrently with itself or vfree() for the
+ * same memory allocation.
+ *
  * Return: pointer to the allocated memory; %NULL if @size is zero or in case of
  *         failure
  */

base-commit: d270beaca6818349b2aed7e6034b800a777087cc