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batman-adv: Broken sync while rescheduling delayed work 

commit abac3ac97f upstream.

Syzkaller got a lot of crashes like:
KASAN: use-after-free Write in *_timers*

All of these crashes point to the same memory area:

The buggy address belongs to the object at ffff88801f870000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 5320 bytes inside of
 8192-byte region [ffff88801f870000, ffff88801f872000)

This area belongs to :
        batadv_priv->batadv_priv_dat->delayed_work->timer_list

The reason for these issues is the lack of synchronization. Delayed
work (batadv_dat_purge) schedules new timer/work while the device
is being deleted. As the result new timer/delayed work is set after
cancel_delayed_work_sync() was called. So after the device is freed
the timer list contains pointer to already freed memory.

Found by Linux Verification Center (linuxtesting.org) with syzkaller.

Cc: stable@kernel.org
Fixes: 2f1dfbe185 ("batman-adv: Distributed ARP Table - implement local storage")
Signed-off-by: Vladislav Efanov <VEfanov@ispras.ru>
Acked-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Vladislav Efanov 2023-05-26 19:16:32 +03:00 committed by Greg Kroah-Hartman
parent 181295bfd8
commit 775ff622dd
1 changed files with 1 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
net/batman-adv/distributed-arp-table.c
View File

@ -101,7 +101,6 @@ static void batadv_dat_purge(struct work_struct *work);
*/
static void batadv_dat_start_timer(struct batadv_priv *bat_priv)
{
INIT_DELAYED_WORK(&bat_priv->dat.work, batadv_dat_purge);
queue_delayed_work(batadv_event_workqueue, &bat_priv->dat.work,
msecs_to_jiffies(10000));
}
@ -819,6 +818,7 @@ int batadv_dat_init(struct batadv_priv *bat_priv)
if (!bat_priv->dat.hash)
return -ENOMEM;
INIT_DELAYED_WORK(&bat_priv->dat.work, batadv_dat_purge);
batadv_dat_start_timer(bat_priv);
batadv_tvlv_handler_register(bat_priv, batadv_dat_tvlv_ogm_handler_v1,