2020-01-13 13:02:18

by Vladis Dronov

Subject: [PATCH] ptp: free ptp device pin descriptors properly

There is a bug in ptp_clock_unregister(), where ptp_cleanup_pin_groups()
first frees ptp->pin_{,dev_}attr, but then posix_clock_unregister() needs
them to destroy a related sysfs device.

These functions can not be just swapped, as posix_clock_unregister() frees
ptp which is needed in the ptp_cleanup_pin_groups(). Fix this by calling
ptp_cleanup_pin_groups() in ptp_clock_release(), right before ptp is freed.

This makes this patch fix an UAF bug in a patch which fixes an UAF bug.

Reported-by: Antti Laakso <[email protected]>
Fixes: a33121e5487b ("ptp: fix the race between the release of ptp_clock and cdev")
Link: https://lore.kernel.org/netdev/[email protected]/
Signed-off-by: Vladis Dronov <[email protected]>
---
drivers/ptp/ptp_clock.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index 61fafe0374ce..b84f16bbd6f2 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -170,6 +170,7 @@ static void ptp_clock_release(struct device *dev)
{
struct ptp_clock *ptp = container_of(dev, struct ptp_clock, dev);

+ ptp_cleanup_pin_groups(ptp);
mutex_destroy(&ptp->tsevq_mux);
mutex_destroy(&ptp->pincfg_mux);
ida_simple_remove(&ptp_clocks_map, ptp->index);
@@ -302,9 +303,8 @@ int ptp_clock_unregister(struct ptp_clock *ptp)
if (ptp->pps_source)
pps_unregister_source(ptp->pps_source);

- ptp_cleanup_pin_groups(ptp);
-
posix_clock_unregister(&ptp->clock);
+
return 0;
}
EXPORT_SYMBOL(ptp_clock_unregister);
--
2.20.1

2020-01-14 04:36:22

by Richard Cochran

Subject: Re: [PATCH] ptp: free ptp device pin descriptors properly

On Mon, Jan 13, 2020 at 02:00:09PM +0100, Vladis Dronov wrote:
> There is a bug in ptp_clock_unregister(), where ptp_cleanup_pin_groups()
> first frees ptp->pin_{,dev_}attr, but then posix_clock_unregister() needs
> them to destroy a related sysfs device.
>
> These functions can not be just swapped, as posix_clock_unregister() frees
> ptp which is needed in the ptp_cleanup_pin_groups(). Fix this by calling
> ptp_cleanup_pin_groups() in ptp_clock_release(), right before ptp is freed.
>
> This makes this patch fix an UAF bug in a patch which fixes an UAF bug.
>
> Reported-by: Antti Laakso <[email protected]>
> Fixes: a33121e5487b ("ptp: fix the race between the release of ptp_clock and cdev")
> Link: https://lore.kernel.org/netdev/[email protected]/
> Signed-off-by: Vladis Dronov <[email protected]>

Acked-by: Richard Cochran <[email protected]>

2020-01-14 19:01:14

by David Miller

Subject: Re: [PATCH] ptp: free ptp device pin descriptors properly

From: Vladis Dronov <[email protected]>
Date: Mon, 13 Jan 2020 14:00:09 +0100

> There is a bug in ptp_clock_unregister(), where ptp_cleanup_pin_groups()
> first frees ptp->pin_{,dev_}attr, but then posix_clock_unregister() needs
> them to destroy a related sysfs device.
>
> These functions can not be just swapped, as posix_clock_unregister() frees
> ptp which is needed in the ptp_cleanup_pin_groups(). Fix this by calling
> ptp_cleanup_pin_groups() in ptp_clock_release(), right before ptp is freed.
>
> This makes this patch fix an UAF bug in a patch which fixes an UAF bug.
>
> Reported-by: Antti Laakso <[email protected]>
> Fixes: a33121e5487b ("ptp: fix the race between the release of ptp_clock and cdev")
> Link: https://lore.kernel.org/netdev/[email protected]/
> Signed-off-by: Vladis Dronov <[email protected]>

Applied, thank you.