[PATCH v6 04/11] mm, arm64: untag user addresses in mm/gup.c

Andrey Konovalov
2018-08-30T15:43:11Z

mm/gup.c provides a kernel interface that accepts user addresses and
manipulates user pages directly (for example get_user_pages, that is used
by the futex syscall). Since a user can provided tagged addresses, we need
to handle such case.

Add untagging to gup.c functions that use user addresses for vma lookup.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
mm/gup.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/mm/gup.c b/mm/gup.c
index 1abc8b4afff6..6f09132c654e 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -666,6 +666,8 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
if (!nr_pages)
return 0;

+ start = untagged_addr(start);
+
VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));

/*
@@ -820,6 +822,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
struct vm_area_struct *vma;
vm_fault_t ret, major = 0;

+ address = untagged_addr(address);
+
if (unlocked)
fault_flags |= FAULT_FLAG_ALLOW_RETRY;

--
2.19.0.rc0.228.g281dcd1b4d0-goog