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From:   Andrey Konovalov <andreyknvl@google.com>
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        Andrey Konovalov <andreyknvl@google.com>
Subject: [PATCH v10 05/12] mm, arm64: untag user pointers in mm/gup.c
Date:   Fri, 22 Feb 2019 13:53:17 +0100
Message-Id: <12759ef1c30887dd9fc7a04498f5a434a67f98d5.1550839937.git.andreyknvl@google.com>
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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 75029649baca..b6eda1608bea 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;
 
-- 
2.21.0.rc0.258.g878e2cd30e-goog