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From: Andrea Arcangeli <aarcange@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: 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 12:15:24 -0400	[thread overview]
Message-ID: <20190820161524.GP31518@redhat.com> (raw)
In-Reply-To: <20190820155948.GA4983@redhat.com>

On Tue, Aug 20, 2019 at 05:59:49PM +0200, Oleg Nesterov wrote:
> On 08/19, Andrea Arcangeli wrote:
> >
> > The proposed fix looks correct, can you resend in a way that can be merged?
> 
> OK, I'll send the same patch to lkml, the only change is s/xxx/still_valid/.

Thanks! Actually I wasn't sure if I should send it myself to avoid
delaying it to next week, but I see you already sent it so problem
solved.

> > It's a bit strange that the file that
> > was opened by the ioctl() syscall gets released
> 
> and this look like another bug we need to investigate,

I did some more debugging in the meanwhile. The current theory is
there are multiple uffd in the same mm and the uffd ctx of the page
fault is not the same uffd ctx of the ioctl that triggers the copy
user.

I'll need to add some more bpftrace code to be sure.

Thanks,
Andrea


  reply	other threads:[~2019-08-20 16:15 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 [this message]
     [not found]           ` <73d7b5b1-a88c-5fca-ba16-be214c2524a4@I-love.SAKURA.ne.jp>
2019-08-20 16:09             ` Oleg Nesterov
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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