There is a bug in ptp_clock_unregister() where pps_unregister_source()
can free up resources needed by posix_clock_unregister() to properly
destroy a related sysfs device.
Fix this by calling pps_unregister_source() in ptp_clock_release().
See also:
commit 75718584cb3c ("ptp: free ptp device pin descriptors properly").
BugLink: https://bugs.launchpad.net/bugs/1864754
Fixes: a33121e5487b ("ptp: fix the race between the release of ptp_clock and cdev")
Tested-by: Piotr Morgwai Kotarbiński <[email protected]>
Signed-off-by: Andrea Righi <[email protected]>
---
v2: move pps_unregister_source() to ptp_clock_release(), instead of
posix_clock_unregister(), that would just introduce a resource leak
drivers/ptp/ptp_clock.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index ac1f2bf9e888..468286ef61ad 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -170,6 +170,9 @@ static void ptp_clock_release(struct device *dev)
{
struct ptp_clock *ptp = container_of(dev, struct ptp_clock, dev);
+ /* Release the clock's resources. */
+ if (ptp->pps_source)
+ pps_unregister_source(ptp->pps_source);
ptp_cleanup_pin_groups(ptp);
mutex_destroy(&ptp->tsevq_mux);
mutex_destroy(&ptp->pincfg_mux);
@@ -298,11 +301,6 @@ int ptp_clock_unregister(struct ptp_clock *ptp)
kthread_cancel_delayed_work_sync(&ptp->aux_work);
kthread_destroy_worker(ptp->kworker);
}
-
- /* Release the clock's resources. */
- if (ptp->pps_source)
- pps_unregister_source(ptp->pps_source);
-
posix_clock_unregister(&ptp->clock);
return 0;
--
2.25.0
On Mon, Mar 09, 2020 at 06:22:38PM +0100, Andrea Righi wrote:
> There is a bug in ptp_clock_unregister() where pps_unregister_source()
> can free up resources needed by posix_clock_unregister() to properly
> destroy a related sysfs device.
This text is inadequate. It does not identify the problem. What
resources? Which related device?
> Fix this by calling pps_unregister_source() in ptp_clock_release().
This statement is redundant, as we can see that from the patch itself.
Instead of saying WHAT the patch does, please explain WHY that fixes
the issue (which, as I said, you still need to identify).
Thanks,
Richard
Hello, Andrea, Colin, all,
This fix is really not needed, as its creation is based on the assumption
that the Ubuntu kernel 5.3.0-40-generic has the upstream commit 75718584cb3c,
which is the real fix to this crash.
> > > I would guess that a kernel in question (5.3.0-40-generic) has the commit
> > > a33121e5487b but does not have the commit 75718584cb3c, which should be
> > > exactly fixing a docking station disconnect crash. Could you please,
> > > check this?
> >
> > Unfortunately the kernel in question already has 75718584cb3c:
> > https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/bionic/commit/?h=hwe&id=c71b774732f997ef38ed7bd62e73891a01f2bbfe
Apologies, but the assumption above is not correct, 5.3.0-40-generic does
not have 75718584cb3c. If it had 75718584cb3c it would be a fix and the ptp-related
crash (described in https://bugs.launchpad.net/bugs/1864754) would not happen.
This way https://lists.ubuntu.com/archives/kernel-team/2020-March/108562.html fix
is not really needed.
Best regards,
Vladis Dronov | Red Hat, Inc. | The Core Kernel | Senior Software Engineer
----- Original Message -----
> From: "Andrea Righi" <[email protected]>
> To: "Richard Cochran" <[email protected]>, "Vladis Dronov" <[email protected]>
> Cc: "David S. Miller" <[email protected]>, [email protected], [email protected]
> Sent: Monday, March 9, 2020 6:22:38 PM
> Subject: [PATCH v2] ptp: free ptp clock properly
>
> There is a bug in ptp_clock_unregister() where pps_unregister_source()
> can free up resources needed by posix_clock_unregister() to properly
> destroy a related sysfs device.
>
> Fix this by calling pps_unregister_source() in ptp_clock_release().
>
> See also:
> commit 75718584cb3c ("ptp: free ptp device pin descriptors properly").
>
> BugLink: https://bugs.launchpad.net/bugs/1864754
> Fixes: a33121e5487b ("ptp: fix the race between the release of ptp_clock and
> cdev")
> Tested-by: Piotr Morgwai Kotarbiński <[email protected]>
> Signed-off-by: Andrea Righi <[email protected]>
> ---
>
> v2: move pps_unregister_source() to ptp_clock_release(), instead of
> posix_clock_unregister(), that would just introduce a resource leak
>
> drivers/ptp/ptp_clock.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
> index ac1f2bf9e888..468286ef61ad 100644
> --- a/drivers/ptp/ptp_clock.c
> +++ b/drivers/ptp/ptp_clock.c
> @@ -170,6 +170,9 @@ static void ptp_clock_release(struct device *dev)
> {
> struct ptp_clock *ptp = container_of(dev, struct ptp_clock, dev);
>
> + /* Release the clock's resources. */
> + if (ptp->pps_source)
> + pps_unregister_source(ptp->pps_source);
> ptp_cleanup_pin_groups(ptp);
> mutex_destroy(&ptp->tsevq_mux);
> mutex_destroy(&ptp->pincfg_mux);
> @@ -298,11 +301,6 @@ int ptp_clock_unregister(struct ptp_clock *ptp)
> kthread_cancel_delayed_work_sync(&ptp->aux_work);
> kthread_destroy_worker(ptp->kworker);
> }
> -
> - /* Release the clock's resources. */
> - if (ptp->pps_source)
> - pps_unregister_source(ptp->pps_source);
> -
> posix_clock_unregister(&ptp->clock);
>
> return 0;
> --
> 2.25.0
On Fri, Apr 03, 2020 at 09:34:14AM -0400, Vladis Dronov wrote:
> Hello, Andrea, Colin, all,
>
> This fix is really not needed, as its creation is based on the assumption
> that the Ubuntu kernel 5.3.0-40-generic has the upstream commit 75718584cb3c,
> which is the real fix to this crash.
>
> > > > I would guess that a kernel in question (5.3.0-40-generic) has the commit
> > > > a33121e5487b but does not have the commit 75718584cb3c, which should be
> > > > exactly fixing a docking station disconnect crash. Could you please,
> > > > check this?
> > >
> > > Unfortunately the kernel in question already has 75718584cb3c:
> > > https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/bionic/commit/?h=hwe&id=c71b774732f997ef38ed7bd62e73891a01f2bbfe
>
> Apologies, but the assumption above is not correct, 5.3.0-40-generic does
> not have 75718584cb3c. If it had 75718584cb3c it would be a fix and the ptp-related
> crash (described in https://bugs.launchpad.net/bugs/1864754) would not happen.
>
> This way https://lists.ubuntu.com/archives/kernel-team/2020-March/108562.html fix
> is not really needed.
Hi Vladis,
for the records, I repeated the tests with a lot of help from the bug
reporter (Morgwai, added in cc), this time making sure we were using the
same kernels.
I confirm that my fix is not really needed as you correctly pointed out.
Thanks for looking into this and sorry for the noise! :)
-Andrea
Hello,
----- Original Message -----
> From: "Andrea Righi" <[email protected]>
> To: "Vladis Dronov" <[email protected]>
> Cc: "Piotr Morgwai Kotarbiński" <[email protected]>, "Colin Ian King" <[email protected]>, "Richard Cochran"
> <[email protected]>, "David S. Miller" <[email protected]>, [email protected],
> [email protected]
> Sent: Tuesday, April 7, 2020 11:34:22 AM
> Subject: Re: [PATCH v2] ptp: free ptp clock properly
>
> On Fri, Apr 03, 2020 at 09:34:14AM -0400, Vladis Dronov wrote:
> > Hello, Andrea, Colin, all,
> >
> > This fix is really not needed, as its creation is based on the assumption
> > that the Ubuntu kernel 5.3.0-40-generic has the upstream commit
> > 75718584cb3c,
> > which is the real fix to this crash.
> >
> > > > > I would guess that a kernel in question (5.3.0-40-generic) has the
> > > > > commit
> > > > > a33121e5487b but does not have the commit 75718584cb3c, which should
> > > > > be
> > > > > exactly fixing a docking station disconnect crash. Could you please,
> > > > > check this?
> > > >
> > > > Unfortunately the kernel in question already has 75718584cb3c:
> > > > https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/bionic/commit/?h=hwe&id=c71b774732f997ef38ed7bd62e73891a01f2bbfe
> >
> > Apologies, but the assumption above is not correct, 5.3.0-40-generic does
> > not have 75718584cb3c. If it had 75718584cb3c it would be a fix and the
> > ptp-related
> > crash (described in https://bugs.launchpad.net/bugs/1864754) would not
> > happen.
> >
> > This way
> > https://lists.ubuntu.com/archives/kernel-team/2020-March/108562.html fix
> > is not really needed.
>
> Hi Vladis,
>
> for the records, I repeated the tests with a lot of help from the bug
> reporter (Morgwai, added in cc), this time making sure we were using the
> same kernels.
>
> I confirm that my fix is not really needed as you correctly pointed out.
> Thanks for looking into this and sorry for the noise! :)
Hei, great! Thank you for updating. I'm happy this situation has resolved
properly!
>
> -Andrea
>
Best regards,
Vladis Dronov | Red Hat, Inc. | The Core Kernel | Senior Software Engineer