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

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Message-Id: <20200122092814.232958966@linuxfoundation.org>
Date:   Wed, 22 Jan 2020 10:29:29 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Antti Laakso <antti.laakso@...el.com>,
        Vladis Dronov <vdronov@...hat.com>,
        Richard Cochran <richardcochran@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.19 073/103] ptp: free ptp device pin descriptors properly

From: Vladis Dronov <vdronov@...hat.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@...el.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@...hat.com>
Acked-by: Richard Cochran <richardcochran@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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);