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Groups > linux.kernel > #1717764

[PATCH 3.18 02/10] audit: Fix use after free in audit_remove_watch_rule()

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3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Kara <jack@suse.cz>

commit d76036ab47eafa6ce52b69482e91ca3ba337d6d6 upstream.

audit_remove_watch_rule() drops watch's reference to parent but then
continues to work with it. That is not safe as parent can get freed once
we drop our reference. The following is a trivial reproducer:

mount -o loop image /mnt
touch /mnt/file
auditctl -w /mnt/file -p wax
umount /mnt
auditctl -D
<crash in fsnotify_destroy_mark()>

Grab our own reference in audit_remove_watch_rule() earlier to make sure
mark does not get freed under us.

Reported-by: Tony Jones <tonyj@suse.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Tested-by: Tony Jones <tonyj@suse.de>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/audit_watch.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/kernel/audit_watch.c
+++ b/kernel/audit_watch.c
@@ -455,13 +455,15 @@ void audit_remove_watch_rule(struct audi
 	list_del(&krule->rlist);
 
 	if (list_empty(&watch->rules)) {
+		/*
+		 * audit_remove_watch() drops our reference to 'parent' which
+		 * can get freed. Grab our own reference to be safe.
+		 */
+		audit_get_parent(parent);
 		audit_remove_watch(watch);
-
-		if (list_empty(&parent->watches)) {
-			audit_get_parent(parent);
+		if (list_empty(&parent->watches))
 			fsnotify_destroy_mark(&parent->mark, audit_watch_group);
-			audit_put_parent(parent);
-		}
+		audit_put_parent(parent);
 	}
 }
 

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[PATCH 3.18 00/10] 3.18.67-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:10 +0200
  [PATCH 3.18 05/10] mm/mempolicy: fix use after free when calling get_mempolicy Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:20 +0200
  [PATCH 3.18 02/10] audit: Fix use after free in audit_remove_watch_rule() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:40 +0200
  [PATCH 3.18 01/10] netfilter: nf_ct_ext: fix possible panic after nf_ct_extend_unregister Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:40 +0200
  [PATCH 3.18 09/10] pids: make task_tgid_nr_ns() safe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:40 +0200
  [PATCH 3.18 06/10] irqchip/atmel-aic: Fix unbalanced of_node_put() in aic_common_irq_fixup() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:40 +0200
  [PATCH 3.18 07/10] irqchip/atmel-aic: Fix unbalanced refcount in aic_common_rtc_irq_fixup() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:40 +0200
  [PATCH 3.18 04/10] ALSA: usb-audio: Apply sample rate quirk to Sennheiser headset Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:40 +0200
  [PATCH 3.18 08/10] Sanitize move_pages() permission checks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:40 +0200
  [PATCH 3.18 10/10] usb: qmi_wwan: add D-Link DWM-222 device ID Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:40 +0200
  Re: [PATCH 3.18 00/10] 3.18.67-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-08-23 02:40 +0200

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