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From: Oleg Nesterov <oleg@redhat.com>
To: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>, linux-mm <linux-mm@kvack.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	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: Wed, 14 Aug 2019 17:10:50 +0200	[thread overview]
Message-ID: <20190814151049.GD11595@redhat.com> (raw)
In-Reply-To: <7e0e4254-17f4-5f07-e9af-097c4162041a@huawei.com>

On 08/14, Kefeng Wang wrote:
>
> On 2019/8/14 21:53, Michal Hocko wrote:
> > On Tue 13-08-19 17:08:05, Kefeng Wang wrote:
> >>
> >> Syzkaller reproducer:
> >> # {Threaded:true Collide:true Repeat:false RepeatTimes:0 Procs:1 Sandbox:none Fault:false FaultCall:-1 FaultNth:0 EnableTun:true EnableNetDev:true EnableNetReset:false EnableCgroups:false EnableBinfmtMisc:true EnableCloseFds:true UseTmpDir:true HandleSegv:true Repro:false Trace:false}
> >> r0 = userfaultfd(0x80800)
> >> ioctl$UFFDIO_API(r0, 0xc018aa3f, &(0x7f0000000200))
> >> ioctl$UFFDIO_REGISTER(r0, 0xc020aa00, &(0x7f0000000080)={{&(0x7f0000ff2000/0xe000)=nil, 0xe000}, 0x1})
> >> ioctl$UFFDIO_COPY(r0, 0xc028aa03, 0x0)
> >> ioctl$UFFDIO_COPY(r0, 0xc028aa03, &(0x7f0000000000)={&(0x7f0000ffc000/0x3000)=nil, &(0x7f0000ffd000/0x2000)=nil, 0x3000})
> >> syz_execute_func(&(0x7f00000000c0)="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")
> >> poll(&(0x7f00000000c0)=[{}], 0x1, 0x0)
> >
> > Is there any way to decypher the above?
>
> no, I also want to know the way :(

perhaps you can run it under strace?

I am wondering if "goto skip_mm" in userfaultfd_release() is correct...
shouldn't it clear VM_UFFD_* and reset vm_userfaultfd_ctx.ctx even if
!mmget_still_valid ?

Oleg.



  reply	other threads:[~2019-08-14 15:11 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 [this message]
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
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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