[PATCH 4.19 073/103] ptp: free ptp device pin descriptors properly

Greg Kroah-Hartman
2020-01-22T09:42:57Z

From: Vladis Dronov <vdronov@redhat.com>

[ Upstream commit 75718584cb3c64e6269109d4d54f888ac5a5fd15 ]

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 <antti.laakso@intel.com>
Fixes: a33121e5487b ("ptp: fix the race between the release of ptp_clock and cdev")
Link: https://lore.kernel.org/netdev/3d2bd09735dbdaf003585ca376b7c1e5b69a19bd.camel@intel.com/
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/ptp/ptp_clock.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -179,6 +179,7 @@ static void ptp_clock_release(struct 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);
@@ -315,9 +316,8 @@ int ptp_clock_unregister(struct ptp_cloc
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);