Re: [PATCH v13 04/20] mm, arm64: untag user pointers passed to memory syscalls

[Steven Rostedt <rostedt@goodmis.org>]

On Thu, 28 Mar 2019 19:10:07 +0100
Andrey Konovalov <andreyknvl@google.com> wrote:

> > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > > ---
> > >  ipc/shm.c      | 2 ++
> > >  mm/madvise.c   | 2 ++
> > >  mm/mempolicy.c | 5 +++++
> > >  mm/migrate.c   | 1 +
> > >  mm/mincore.c   | 2 ++
> > >  mm/mlock.c     | 5 +++++
> > >  mm/mmap.c      | 7 +++++++
> > >  mm/mprotect.c  | 1 +
> > >  mm/mremap.c    | 2 ++
> > >  mm/msync.c     | 2 ++
> > >  10 files changed, 29 insertions(+)  
> >
> > I wonder whether it's better to keep these as wrappers in the arm64
> > code.  
> 
> I don't think I understand what you propose, could you elaborate?

I believe Catalin is saying that instead of placing things like:

@@ -1593,6 +1593,7 @@ SYSCALL_DEFINE3(shmat, int, shmid, char __user *, shmaddr, int, shmflg)
 	unsigned long ret;
 	long err;
 
+	shmaddr = untagged_addr(shmaddr);

To instead have the shmaddr set to the untagged_addr() before calling
the system call, and passing the untagged addr to the system call, as
that goes through the arm64 architecture specific code first.

-- Steve
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