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Message-Id: <20220418121145.301779931@linuxfoundation.org>
Date: Mon, 18 Apr 2022 14:12:04 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Lin Ma <linma@....edu.cn>,
"David S. Miller" <davem@...emloft.net>,
Xu Jia <xujia39@...wei.com>
Subject: [PATCH 5.10 002/105] hamradio: defer 6pack kfree after unregister_netdev
From: Lin Ma <linma@....edu.cn>
commit 0b9111922b1f399aba6ed1e1b8f2079c3da1aed8 upstream.
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@....edu.cn>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Xu Jia <xujia39@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
drivers/net/hamradio/6pack.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c
@@ -679,9 +679,11 @@ static void sixpack_close(struct tty_str
del_timer_sync(&sp->tx_t);
del_timer_sync(&sp->resync_t);
- /* Free all 6pack frame buffers. */
+ /* Free all 6pack frame buffers after unreg. */
kfree(sp->rbuff);
kfree(sp->xbuff);
+
+ free_netdev(sp->dev);
}
/* Perform I/O control on an active 6pack channel. */
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