From: Oleg Nesterov <oleg@redhat.com>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
Kefeng Wang <wangkefeng.wang@huawei.com>,
Michal Hocko <mhocko@suse.com>, linux-mm <linux-mm@kvack.org>,
Peter Xu <peterx@redhat.com>, Mike Rapoport <rppt@linux.ibm.com>,
Jann Horn <jannh@google.com>, Jason Gunthorpe <jgg@mellanox.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [BUG] kernel BUG at fs/userfaultfd.c:385 after 04f5866e41fb
Date: Tue, 20 Aug 2019 18:09:36 +0200 [thread overview]
Message-ID: <20190820160936.GC4983@redhat.com> (raw)
In-Reply-To: <73d7b5b1-a88c-5fca-ba16-be214c2524a4@I-love.SAKURA.ne.jp>
On 08/20, Tetsuo Handa wrote:
>
> On 2019/08/20 1:05, Andrea Arcangeli wrote:
> > It's a bit strange that the file that
> > was opened by the ioctl() syscall gets released and its
> > file->private_data destroyed before the ioctl syscall has a chance to
> > return to userland.
>
> My guess is that the fd was opened by userfaultfd() syscall, and the fd was
> closed by close() syscall. Nothing wrong. But when a page fault happened,
The problem is that this page fault is triggered by ioctl() and this file
was already closed and the final fput() was already called, note that
userfaultfd_release() is f_op->release.
> Then, not resetting pointer to the data structure before
> releasing the memory (due to "goto skip_mm;") is the bug.
Yes, this is wrong in any case and this is that the patch tries to fix.
Oleg.
next prev parent reply other threads:[~2019-08-20 16:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-13 9:08 [BUG] kernel BUG at fs/userfaultfd.c:385 after 04f5866e41fb Kefeng Wang
2019-08-14 13:53 ` Michal Hocko
2019-08-14 14:45 ` Kefeng Wang
2019-08-14 15:10 ` Oleg Nesterov
2019-08-14 15:41 ` Oleg Nesterov
2019-08-15 2:21 ` Kefeng Wang
2019-08-15 9:54 ` Oleg Nesterov
2019-08-16 10:37 ` Kefeng Wang
2019-08-19 12:48 ` Oleg Nesterov
2019-08-19 16:05 ` Andrea Arcangeli
2019-08-20 15:59 ` Oleg Nesterov
2019-08-20 16:15 ` Andrea Arcangeli
[not found] ` <73d7b5b1-a88c-5fca-ba16-be214c2524a4@I-love.SAKURA.ne.jp>
2019-08-20 16:09 ` Oleg Nesterov [this message]
2019-08-20 16:02 ` [PATCH] userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx Oleg Nesterov
2019-08-20 16:05 ` Andrea Arcangeli
2019-08-21 0:53 ` Kefeng Wang
2019-08-27 16:33 ` [BUG] kernel BUG at fs/userfaultfd.c:385 after 04f5866e41fb Oleg Nesterov
2019-08-27 17:14 ` Andrea Arcangeli
2019-08-28 14:25 ` Oleg Nesterov
2019-08-29 12:05 ` Andrea Arcangeli
2019-08-30 16:49 ` Oleg Nesterov
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