From: Lin Ma <linma@zju.edu.cn> mainline inclusion from mainline-v5.16-rc1 commit 0b9111922b1f399aba6ed1e1b8f2079c3da1aed8 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5224J CVE: CVE-2022-1198 -------------------------------- 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> Signed-off-by: Xu Jia <xujia39@huawei.com> Reviewed-by: Wei Yongjun <weiyongjun1@huawei.com> Reviewed-by: Wang Weiyang <wangweiyang2@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- 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 bd0beb16d68a..8221f7c2709e 100644 --- a/drivers/net/hamradio/6pack.c +++ b/drivers/net/hamradio/6pack.c @@ -677,11 +677,13 @@ 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. */ -- 2.20.1