[PATCH v9 4/8] mm, arm64: untag user addresses in mm/gup.c

[Andrey Konovalov]

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 <andreyk...@google.com>
---
 mm/gup.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/gup.c b/mm/gup.c
index 8cb68a50dbdf..409aedb1e2d5 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -683,6 +683,8 @@ 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));
 
        /*
@@ -845,6 +847,8 @@ 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;
 
-- 
2.20.0.rc2.403.gdbc3b29805-goog