From 0b9111922b1f399aba6ed1e1b8f2079c3da1aed8 Mon Sep 17 00:00:00 2001
From: Lin Ma <linma@zju.edu.cn>
Date: Mon, 8 Nov 2021 18:37:59 +0800
Subject: [PATCH] hamradio: defer 6pack kfree after unregister_netdev
Git-commit: 0b9111922b1f399aba6ed1e1b8f2079c3da1aed8
Patch-mainline: v5.16-rc1
References: CVE-2022-1195 bsc#1198029
There is a possible race condition (use-after-free) like below
(USE) | (FREE)
dev_queue_xmit |
__dev_queue_xmit |
__dev_xmit_skb |
sch_direct_xmit | ...
xmit_one |
netdev_start_xmit | tty_ldisc_kill
__netdev_start_xmit | 6pack_close
sp_xmit | kfree
sp_encaps |
|
According to the patch "defer ax25 kfree after unregister_netdev", this
patch reorder the kfree after the unregister_netdev to avoid the possible
UAF as the unregister_netdev() is well synchronized and won't return if
there is a running routine.
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/net/hamradio/6pack.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index f4e8793e995d..fb0a3825edd0 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c
@@ -672,11 +672,13 @@ static void sixpack_close(struct tty_struct *tty)
del_timer_sync(&sp->tx_t);
del_timer_sync(&sp->resync_t);
- /* Free all 6pack frame buffers. */
+ unregister_netdev(sp->dev);
+
+ /* Free all 6pack frame buffers after unreg. */
kfree(sp->rbuff);
kfree(sp->xbuff);
- unregister_netdev(sp->dev);
+ free_netdev(sp->dev);
}
/* Perform I/O control on an active 6pack channel. */
--
2.31.1