[PATCH v14 07/17] mm, arm64: untag user pointers in mm/gup.c
Andrey Konovalov
andreyknvl at google.com
Tue Apr 30 13:25:03 UTC 2019
This patch is a part of a series that extends arm64 kernel ABI to allow to
pass tagged user pointers (with the top byte set to something else other
than 0x00) as syscall arguments.
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 this case.
Add untagging to gup.c functions that use user addresses for vma lookups.
Signed-off-by: Andrey Konovalov <andreyknvl at google.com>
---
mm/gup.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/mm/gup.c b/mm/gup.c
index 91819b8ad9cc..2f477a0a7180 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -696,6 +696,8 @@ 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));
/*
@@ -858,6 +860,8 @@ 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;
--
2.21.0.593.g511ec345e18-goog
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