coredump: fix race condition between collapse_huge_page() and core dumping

[thirdparty/kernel/stable.git] / include / linux / sched / mm.h

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index a3fda9f024c3c1988b6ff60954d7f7e74a9c1ecf..4a7944078cc35dddcea4963f1099e81d147c6936 100644 (file)
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -54,6 +54,10 @@ static inline void mmdrop(struct mm_struct *mm)
  * followed by taking the mmap_sem for writing before modifying the
  * vmas or anything the coredump pretends not to change from under it.
  *
+ * It also has to be called when mmgrab() is used in the context of
+ * the process, but then the mm_count refcount is transferred outside
+ * the context of the process to run down_write() on that pinned mm.
+ *
  * NOTE: find_extend_vma() called from GUP context is the only place
  * that can modify the "mm" (notably the vm_start/end) under mmap_sem
  * for reading and outside the context of the process, so it is also