diff options
| -rw-r--r-- | mm/memory.c | 10 |
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(); |