* [PATCH] usblp: fix race between disconnect() and read()
@ 2020-09-17 10:34 Oliver Neukum
2020-09-17 11:43 ` Greg KH
0 siblings, 1 reply; 4+ messages in thread
From: Oliver Neukum @ 2020-09-17 10:34 UTC (permalink / raw)
To: gregKH, linux-usb; +Cc: Oliver Neukum
read() needs to check whether the device has been
disconnected before it tries to talk to the device.
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reported-by: syzbot+be5b5f86a162a6c281e6@syzkaller.appspotmail.com
---
drivers/usb/class/usblp.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index 084c48c5848f..67cbd42421be 100644
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -827,6 +827,11 @@ static ssize_t usblp_read(struct file *file, char __user *buffer, size_t len, lo
if (rv < 0)
return rv;
+ if (!usblp->present) {
+ count = -ENODEV;
+ goto done;
+ }
+
if ((avail = usblp->rstatus) < 0) {
printk(KERN_ERR "usblp%d: error %d reading from printer\n",
usblp->minor, (int)avail);
--
2.16.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] usblp: fix race between disconnect() and read()
2020-09-17 10:34 [PATCH] usblp: fix race between disconnect() and read() Oliver Neukum
@ 2020-09-17 11:43 ` Greg KH
2020-09-17 12:03 ` Oliver Neukum
0 siblings, 1 reply; 4+ messages in thread
From: Greg KH @ 2020-09-17 11:43 UTC (permalink / raw)
To: Oliver Neukum; +Cc: linux-usb
On Thu, Sep 17, 2020 at 12:34:27PM +0200, Oliver Neukum wrote:
> read() needs to check whether the device has been
> disconnected before it tries to talk to the device.
>
> Signed-off-by: Oliver Neukum <oneukum@suse.com>
> Reported-by: syzbot+be5b5f86a162a6c281e6@syzkaller.appspotmail.com
> ---
> drivers/usb/class/usblp.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
> index 084c48c5848f..67cbd42421be 100644
> --- a/drivers/usb/class/usblp.c
> +++ b/drivers/usb/class/usblp.c
> @@ -827,6 +827,11 @@ static ssize_t usblp_read(struct file *file, char __user *buffer, size_t len, lo
> if (rv < 0)
> return rv;
>
> + if (!usblp->present) {
> + count = -ENODEV;
> + goto done;
> + }
> +
What prevents ->present from not being changed right after this test?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] usblp: fix race between disconnect() and read()
2020-09-17 11:43 ` Greg KH
@ 2020-09-17 12:03 ` Oliver Neukum
2020-09-17 16:45 ` Greg KH
0 siblings, 1 reply; 4+ messages in thread
From: Oliver Neukum @ 2020-09-17 12:03 UTC (permalink / raw)
To: Greg KH; +Cc: linux-usb
Am Donnerstag, den 17.09.2020, 13:43 +0200 schrieb Greg KH:
> On Thu, Sep 17, 2020 at 12:34:27PM +0200, Oliver Neukum wrote:
> > read() needs to check whether the device has been
> > disconnected before it tries to talk to the device.
> >
> > Signed-off-by: Oliver Neukum <oneukum@suse.com>
> > Reported-by: syzbot+be5b5f86a162a6c281e6@syzkaller.appspotmail.com
> > ---
> > drivers/usb/class/usblp.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
> > index 084c48c5848f..67cbd42421be 100644
> > --- a/drivers/usb/class/usblp.c
> > +++ b/drivers/usb/class/usblp.c
> > @@ -827,6 +827,11 @@ static ssize_t usblp_read(struct file *file, char __user *buffer, size_t len, lo
> > if (rv < 0)
> > return rv;
> >
> > + if (!usblp->present) {
> > + count = -ENODEV;
> > + goto done;
> > + }
> > +
>
> What prevents ->present from not being changed right after this test?
Hi,
the mutex taken in
rv = usblp_rwait_and_lock(usblp, !!(file->f_flags & O_NONBLOCK));
right above it. Yes, this driver is a mess. But short of adding
a ton of comments or rewriting the whole thing I have no idea
what to do about that.
Regards
Oliver
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] usblp: fix race between disconnect() and read()
2020-09-17 12:03 ` Oliver Neukum
@ 2020-09-17 16:45 ` Greg KH
0 siblings, 0 replies; 4+ messages in thread
From: Greg KH @ 2020-09-17 16:45 UTC (permalink / raw)
To: Oliver Neukum; +Cc: linux-usb
On Thu, Sep 17, 2020 at 02:03:11PM +0200, Oliver Neukum wrote:
> Am Donnerstag, den 17.09.2020, 13:43 +0200 schrieb Greg KH:
> > On Thu, Sep 17, 2020 at 12:34:27PM +0200, Oliver Neukum wrote:
> > > read() needs to check whether the device has been
> > > disconnected before it tries to talk to the device.
> > >
> > > Signed-off-by: Oliver Neukum <oneukum@suse.com>
> > > Reported-by: syzbot+be5b5f86a162a6c281e6@syzkaller.appspotmail.com
> > > ---
> > > drivers/usb/class/usblp.c | 5 +++++
> > > 1 file changed, 5 insertions(+)
> > >
> > > diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
> > > index 084c48c5848f..67cbd42421be 100644
> > > --- a/drivers/usb/class/usblp.c
> > > +++ b/drivers/usb/class/usblp.c
> > > @@ -827,6 +827,11 @@ static ssize_t usblp_read(struct file *file, char __user *buffer, size_t len, lo
> > > if (rv < 0)
> > > return rv;
> > >
> > > + if (!usblp->present) {
> > > + count = -ENODEV;
> > > + goto done;
> > > + }
> > > +
> >
> > What prevents ->present from not being changed right after this test?
>
> Hi,
>
> the mutex taken in
>
> rv = usblp_rwait_and_lock(usblp, !!(file->f_flags & O_NONBLOCK));
Ah, missed that, thanks.
greg k-h
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-09-17 16:46 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2020-09-17 10:34 [PATCH] usblp: fix race between disconnect() and read() Oliver Neukum
2020-09-17 11:43 ` Greg KH
2020-09-17 12:03 ` Oliver Neukum
2020-09-17 16:45 ` Greg KH
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