From: Jason Gunthorpe <email@example.com> To: Dmitry Vyukov <firstname.lastname@example.org> Cc: syzbot <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Subject: Re: [syzbot] KASAN: use-after-free Read in addr_handler (4) Date: Thu, 16 Sep 2021 10:04:59 -0300 [thread overview] Message-ID: <20210916130459.GJ3544071@ziepe.ca> (raw) In-Reply-To: <CACT4Y+bxDuLggCzkLAchrGkKQxC2v4bhc01ciBg+oc17q2=HHw@mail.gmail.com> On Thu, Sep 16, 2021 at 09:43:19AM +0200, Dmitry Vyukov wrote: > On Wed, 15 Sept 2021 at 21:36, Jason Gunthorpe <email@example.com> wrote: > > > > On Wed, Sep 15, 2021 at 05:41:22AM -0700, syzbot wrote: > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: 926de8c4326c Merge tag 'acpi-5.15-rc1-3' of git://git.kern.. > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=11fd67ed300000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=37df9ef5660a8387 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=dc3dfba010d7671e05f5 > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1 > > > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: firstname.lastname@example.org > > > > #syz dup: KASAN: use-after-free Write in addr_resolve (2) > > > > Frankly, I still can't figure out how this is happening > > > > RDMA_USER_CM_CMD_RESOLVE_IP triggers a background work and > > RDMA_USER_CM_CMD_DESTROY_ID triggers destruction of the memory the > > work touches. > > > > rdma_addr_cancel() is supposed to ensure that the work isn't and won't > > run. > > > > So to hit this we have to either not call rdma_addr_cancel() when it > > is need, or rdma_addr_cancel() has to be broken and continue to allow > > the work. > > > > I could find nothing along either path, though rdma_addr_cancel() > > relies on some complicated properties of the workqueues I'm not > > entirely positive about. > > I stared at the code, but it's too complex to grasp it all entirely. > There are definitely lots of tricky concurrent state transitions and > potential for unexpected interleavings. My bet would be on some tricky > hard-to-trigger thread interleaving. From a uapi perspective the entire thing is serialized with a mutex.. > The only thing I can think of is adding more WARNINGs to the code to > check more of these assumptions. But I don't know if there are any > useful testable assumptions... Do you have any idea why we can't get a reproduction out of syzkaller here? I feel less comfortable with syzkaller's debug output, can you give some idea what it might be doing concurrently? Jason
next prev parent reply other threads:[~2021-09-16 13:05 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-09-15 12:41 syzbot 2021-09-15 19:36 ` Jason Gunthorpe 2021-09-16 7:43 ` Dmitry Vyukov 2021-09-16 13:04 ` Jason Gunthorpe [this message] 2021-09-16 14:45 ` Dmitry Vyukov 2021-09-16 14:47 ` Dmitry Vyukov 2021-09-16 14:55 ` Dmitry Vyukov 2021-09-16 15:08 ` Jason Gunthorpe 2021-09-16 15:17 ` Dmitry Vyukov 2021-09-16 16:02 ` Jason Gunthorpe 2021-09-16 16:28 ` Jason Gunthorpe 2021-09-20 8:13 ` Dmitry Vyukov [not found] ` <email@example.com> 2021-10-05 12:23 ` Jason Gunthorpe [not found] ` <firstname.lastname@example.org> 2021-10-06 11:41 ` Jason Gunthorpe
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