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-rw-r--r--fs/userfaultfd.c29
1 files changed, 21 insertions, 8 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index f7555fc25877..1d622f276e3a 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -340,9 +340,28 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason)
bool must_wait, return_to_userland;
long blocking_state;
- BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
-
ret = VM_FAULT_SIGBUS;
+
+ /*
+ * We don't do userfault handling for the final child pid update.
+ *
+ * We also don't do userfault handling during
+ * coredumping. hugetlbfs has the special
+ * follow_hugetlb_page() to skip missing pages in the
+ * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with
+ * the no_page_table() helper in follow_page_mask(), but the
+ * shmem_vm_ops->fault method is invoked even during
+ * coredumping without mmap_sem and it ends up here.
+ */
+ if (current->flags & (PF_EXITING|PF_DUMPCORE))
+ goto out;
+
+ /*
+ * Coredumping runs without mmap_sem so we can only check that
+ * the mmap_sem is held, if PF_DUMPCORE was not set.
+ */
+ WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
+
ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
if (!ctx)
goto out;
@@ -361,12 +380,6 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason)
goto out;
/*
- * We don't do userfault handling for the final child pid update.
- */
- if (current->flags & PF_EXITING)
- goto out;
-
- /*
* Check that we can return VM_FAULT_RETRY.
*
* NOTE: it should become possible to return VM_FAULT_RETRY