1 files changed, 8 insertions, 2 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 122d965e820f..f594bb65a9f1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1264,9 +1264,15 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 				 * do_wp_page has broken COW when necessary,
 				 * even if maybe_mkwrite decided not to set
 				 * pte_write. We can thus safely do subsequent
-				 * page lookups as if they were reads.
+				 * page lookups as if they were reads. But only
+				 * do so when looping for pte_write is futile:
+				 * in some cases userspace may also be wanting
+				 * to write to the gotten user page, which a
+				 * read fault here might prevent (a readonly
+				 * page might get reCOWed by userspace write).
 				 */
-				if (ret & VM_FAULT_WRITE)
+				if ((ret & VM_FAULT_WRITE) &&
+				    !(vma->vm_flags & VM_WRITE))
 					foll_flags &= ~FOLL_WRITE;
 
 				cond_resched();