linux-kernel - Re: WARNING in pvr2_i2c_core

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Message-ID: <CAOEiV1ehZoknZ6b-DOjYxwH2F8UpXO3WXByuM_FcPDOy6=RSSA@mail.gmail.com>
Date:   Wed, 22 Jul 2020 14:48:44 +0530
From:   B K Karthik <bk.bk2000.kb@...il.com>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Markus.Elfring@....de, andreyknvl@...gle.com,
        bkkarthik@...u.pes.edu, dan.carpenter@...cle.com,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, rafael@...nel.org,
        syzkaller-bugs@...glegroups.com,
        syzbot <syzbot+e74a998ca8f1df9cc332@...kaller.appspotmail.com>
Subject: Re: WARNING in pvr2_i2c_core_done

On Wed, 22 Jul 2020 at 14:42, Hillf Danton <hdanton@...a.com> wrote:
>
>
> From: syzbot <syzbot+e74a998ca8f1df9cc332@...kaller.appspotmail.com>
>
> Tue, 21 Jul 2020 21:06:10 -0700
> > Hello,
> >
> > syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> > general protection fault in kernfs_find_ns
> >
> > pvrusb2: Invalid write control endpoint
> > pvrusb2: Invalid write control endpoint
> > pvrusb2: Invalid write control endpoint
> > pvrusb2: Invalid write control endpoint
> > general protection fault, probably for non-canonical address 0xdffffc000000000e: 0000 [#1] SMP KASAN
> > KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077]
> > CPU: 0 PID: 78 Comm: pvrusb2-context Not tainted 5.7.0-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > RIP: 0010:kernfs_find_ns+0x31/0x370 fs/kernfs/dir.c:829
> > Code: 49 89 d6 41 55 41 54 55 48 89 fd 53 48 83 ec 08 e8 f4 61 af ff 48 8d 7d 70 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 1e 03 00 00 48 8d bd 98 00 00 00 48 8b 5d 70 48
> > RSP: 0018:ffff8881d419f938 EFLAGS: 00010202
> > RAX: dffffc0000000000 RBX: ffffffff863789c0 RCX: ffffffff85a79ba7
> > RDX: 000000000000000e RSI: ffffffff81901d1c RDI: 0000000000000070
> > RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff873ed1e7
> > R10: fffffbfff0e7da3c R11: 0000000000000001 R12: 0000000000000000
> > R13: 0000000000000000 R14: 0000000000000000 R15: ffffffff863790e0
> > FS:  0000000000000000(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007f3a7e248000 CR3: 00000001d2224000 CR4: 00000000001406f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >  kernfs_find_and_get_ns+0x2f/0x60 fs/kernfs/dir.c:906
> >  kernfs_find_and_get include/linux/kernfs.h:548 [inline]
> >  sysfs_unmerge_group+0x5d/0x160 fs/sysfs/group.c:366
> >  dpm_sysfs_remove+0x62/0xb0 drivers/base/power/sysfs.c:790
>
> [3]
>
> >  device_del+0x18b/0xd20 drivers/base/core.c:2834
> >  device_unregister+0x22/0xc0 drivers/base/core.c:2889
> >  i2c_unregister_device include/linux/err.h:41 [inline]
>
> [2]
>
> >  i2c_client_dev_release+0x39/0x50 drivers/i2c/i2c-core-base.c:465
> >  device_release+0x71/0x200 drivers/base/core.c:1559
>
> [1] kobject_del() goes before the release cb in kobject_cleanup() and
> kobj is removed from sysfs, see [3] above.

Oh, thank you for letting me know about this. Forgive me, but I did
not understand you very clearly.
I presume you are saying that the second call to
i2c_unregister_device() is where the problem occurs?

please let me know.
thanks,

karthik