userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx
authorOleg Nesterov <oleg@redhat.com>
Sun, 25 Aug 2019 00:54:56 +0000 (17:54 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 29 Aug 2019 06:26:43 +0000 (08:26 +0200)
commitbc2a69242f707891d8c6ef98e3ed4dad32a5f37e
treedb6965086cbe26d636ac64885bff7baed96294bd
parent0570fc57e3421f6b3196691bfd766a01d481bc27
userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx

commit 46d0b24c5ee10a15dfb25e20642f5a5ed59c5003 upstream.

userfaultfd_release() should clear vm_flags/vm_userfaultfd_ctx even if
mm->core_state != NULL.

Otherwise a page fault can see userfaultfd_missing() == T and use an
already freed userfaultfd_ctx.

Link: http://lkml.kernel.org/r/20190820160237.GB4983@redhat.com
Fixes: 04f5866e41fb ("coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Tested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/userfaultfd.c