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[v8,4/8] mm, arm64: untag user addresses in mm/gup.c

Message ID f4c83a89817a81d741373d3fb529864d3a3bd61e.1541687720.git.andreyknvl@google.com (mailing list archive)
State New, archived
Headers show
Series arm64: untag user pointers passed to the kernel | expand

Commit Message

Andrey Konovalov Nov. 8, 2018, 2:36 p.m. UTC 
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(+)
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Patch

diff --git a/mm/gup.c b/mm/gup.c
index f76e77a2d34b..6ff310818616 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -677,6 +677,8 @@  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));
 
 	/*
@@ -840,6 +842,8 @@  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;