On 6/12/19 5:43 AM, Andrey Konovalov wrote: > 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. > > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> > Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > --- Reviewed-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx> > mm/gup.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/gup.c b/mm/gup.c > index ddde097cf9e4..c37df3d455a2 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -802,6 +802,8 @@ 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)); > > /* > @@ -964,6 +966,8 @@ 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; > >
