Re: [PATCH 1/1] userfaultfd: hugetlbfs: prevent UFFDIO_COPY to fill beyond the end of i_size

[Andrea Arcangeli <aarcange@redhat.com>]

On Mon, Oct 16, 2017 at 04:14:43PM -0700, Andrew Morton wrote:
> On Tue, 17 Oct 2017 00:39:14 +0200 Andrea Arcangeli <aarcange@redhat.com> wrote:
> 
> > kernel BUG at fs/hugetlbfs/inode.c:484!
> > RIP: 0010:[<ffffffff815f8520>]  [<ffffffff815f8520>] remove_inode_hugepages+0x3d0/0x410
> > Call Trace:
> >  [<ffffffff815f95b9>] hugetlbfs_setattr+0xd9/0x130
> >  [<ffffffff81526312>] notify_change+0x292/0x410
> >  [<ffffffff816cc6b6>] ? security_inode_need_killpriv+0x16/0x20
> >  [<ffffffff81503c65>] do_truncate+0x65/0xa0
> >  [<ffffffff81504035>] ? do_sys_ftruncate.constprop.3+0xe5/0x180
> >  [<ffffffff8150406a>] do_sys_ftruncate.constprop.3+0x11a/0x180
> >  [<ffffffff8150410e>] SyS_ftruncate+0xe/0x10
> >  [<ffffffff81999f27>] tracesys+0xd9/0xde
> > 
> > This oops was caused by the lack of i_size check in
> > hugetlb_mcopy_atomic_pte. mmap() can still succeed beyond the end of
> > the i_size after vmtruncate zapped vmas in those ranges, but the
> > faults must not succeed, and that includes UFFDIO_COPY.
> > 
> > We could differentiate the retval to userland to represent a SIGBUS
> > like a page fault would do (vs SIGSEGV), but it doesn't seem very
> > useful and we'd need to pick a random retval as there's no meaningful
> > syscall retval that would differentiate from SIGSEGV and SIGBUS,
> > there's just -EFAULT.
> > 
> > Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> > Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> 
> No cc:stable?  The patch applies to 4.13 textually...

Yes, I should have CC'ed stable.

Last time I CC'ed stable I didn't submit it in the right way, I should
have added cc:stable to the commit body, this time. I can resend with
cc:stable if you prefer.

Thanks!
Andrea

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