There really should be no circumstances under which a non-FOLL_NOWAIT GUP
operation fails to return any pages, so make this an error and warn on it.
To catch the trivial case, simply exit early if nr_pages == 0.
This brings __get_user_pages_locked() in line with the behaviour of its
nommu variant.
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
---
mm/gup.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/mm/gup.c b/mm/gup.c
index b21b33d1787e..231711efa390 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1471,6 +1471,9 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
long ret, pages_done;
bool must_unlock = false;
+ if (!nr_pages)
+ return 0;
+
/*
* The internal caller expects GUP to manage the lock internally and the
* lock must be released when this returns.
@@ -1595,6 +1598,14 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
mmap_read_unlock(mm);
*locked = 0;
}
+
+ /*
+ * Failing to pin anything implies something has gone wrong (except when
+ * FOLL_NOWAIT is specified).
+ */
+ if (WARN_ON_ONCE(pages_done == 0 && !(flags & FOLL_NOWAIT)))
+ return -EFAULT;
+
return pages_done;
}
--
2.42.0