linux-kernel - Re: KASAN: use-after-free Read in sg

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Message-ID: <CAB7eexKm-0eO11KO2Brp_djcgXHO=1gARfkUN13ZV8BNHBxURw@mail.gmail.com>
Date:   Thu, 29 Sep 2022 11:01:27 +0800
From:   Rondreis <linhaoguo86@...il.com>
To:     dgilbert@...erlog.com
Cc:     Tony Battersby <tonyb@...ernetics.com>, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: KASAN: use-after-free Read in sg_release

Thank you for your solution! I am sorry that I was not able to extract
the reproducer. But I am improving the solution to reproduce the crash.
If I succeed in reproducing it, I will check it for you as soon as possible!

Best Regards,
Rondreis

On Thu, Sep 29, 2022 at 5:45 AM Douglas Gilbert <dgilbert@...erlog.com> wrote:
>
> On 2022-09-22 17:29, Tony Battersby wrote:
> > On 9/20/22 10:46, Rondreis wrote:
> >> Hello,
> >>
> >> When fuzzing the Linux kernel driver v6.0-rc6, the following crash was
> >> triggered.
> >>
> >> HEAD commit: 521a547ced6477c54b4b0cc206000406c221b4d6
> >> git tree: upstream
> >>
> >> kernel config: https://pastebin.com/raw/hekxU61F
> >> console output: https://pastebin.com/raw/73a8RzBY
> >>
> >> Sorry for failing to extract the reproducer. But on other versions of
> >> Linux, I also triggered this crash.
> >>
> >> I would appreciate it if you have any idea how to solve this bug.
> >>
> > sg_release() calls "kref_put(&sfp->f_ref, sg_remove_sfp)" which
> > eventually does "kref_put(&sdp->d_ref, sg_device_destroy)" which does
> > "kfree(sdp)", but sg_release() continues to access sdp afterward.  Try
> > the following patch.
> >
> >>From 82ca6785c40eded6229183a53752fc5e43db4a94 Mon Sep 17 00:00:00 2001
> > From: Tony Battersby <tonyb@...ernetics.com>
> > Date: Thu, 22 Sep 2022 11:05:30 -0400
> > Subject: [PATCH] scsi: sg: fix memory-use-after-free on device removal
> >
> > Fix memory-use-after-free race when closing a sg fd to a removed device.
> >
> > Link: https://lore.kernel.org/linux-scsi/CAB7eexK_jr1LWOO9RWrBF9as7gAS9kpHjrZFRuRrRJF=1H4W6A@mail.gmail.com/
> > Reported-by: Rondreis <linhaoguo86@...il.com>
> > Cc: <stable@...r.kernel.org>
> > Signed-off-by: Tony Battersby <tonyb@...ernetics.com>
> > ---
> >   drivers/scsi/sg.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> > index 340b050ad28d..f44cbe42dba9 100644
> > --- a/drivers/scsi/sg.c
> > +++ b/drivers/scsi/sg.c
> > @@ -388,6 +388,7 @@ sg_release(struct inode *inode, struct file *filp)
> >               return -ENXIO;
> >       SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp, "sg_release\n"));
> >
> > +     kref_get(&sdp->d_ref);
> >       mutex_lock(&sdp->open_rel_lock);
> >       scsi_autopm_put_device(sdp->device);
> >       kref_put(&sfp->f_ref, sg_remove_sfp);
> > @@ -402,6 +403,7 @@ sg_release(struct inode *inode, struct file *filp)
> >               wake_up_interruptible(&sdp->open_wait);
> >       }
> >       mutex_unlock(&sdp->open_rel_lock);
> > +     kref_put(&sdp->d_ref, sg_device_destroy);
> >       return 0;
> >   }
> >
>
>
> Hi Rondreis,
> Have you been able to test the above patch from Tony?
>
> Doug Gilbert
>