From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Lin Ma <linma@zju.edu.cn>,
"David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 17/19] hamradio: defer ax25 kfree after unregister_netdev
Date: Mon, 27 Dec 2021 16:27:19 +0100 [thread overview]
Message-ID: <20211227151317.107250211@linuxfoundation.org> (raw)
In-Reply-To: <20211227151316.558965545@linuxfoundation.org>
From: Lin Ma <linma@zju.edu.cn>
commit 3e0588c291d6ce225f2b891753ca41d45ba42469 upstream.
There is a possible race condition (use-after-free) like below
(USE) | (FREE)
ax25_sendmsg |
ax25_queue_xmit |
dev_queue_xmit |
__dev_queue_xmit |
__dev_xmit_skb |
sch_direct_xmit | ...
xmit_one |
netdev_start_xmit | tty_ldisc_kill
__netdev_start_xmit | mkiss_close
ax_xmit | kfree
ax_encaps |
|
Even though there are two synchronization primitives before the kfree:
1. wait_for_completion(&ax->dead). This can prevent the race with
routines from mkiss_ioctl. However, it cannot stop the routine coming
from upper layer, i.e., the ax25_sendmsg.
2. netif_stop_queue(ax->dev). It seems that this line of code aims to
halt the transmit queue but it fails to stop the routine that already
being xmit.
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/hamradio/mkiss.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/drivers/net/hamradio/mkiss.c
+++ b/drivers/net/hamradio/mkiss.c
@@ -803,13 +803,14 @@ static void mkiss_close(struct tty_struc
*/
netif_stop_queue(ax->dev);
- /* Free all AX25 frame buffers. */
- kfree(ax->rbuff);
- kfree(ax->xbuff);
-
ax->tty = NULL;
unregister_netdev(ax->dev);
+
+ /* Free all AX25 frame buffers after unreg. */
+ kfree(ax->rbuff);
+ kfree(ax->xbuff);
+
free_netdev(ax->dev);
}
next prev parent reply other threads:[~2021-12-27 15:29 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-27 15:27 [PATCH 4.9 00/19] 4.9.295-rc1 review Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 01/19] net: usb: lan78xx: add Allied Telesis AT29M2-AF Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 02/19] can: kvaser_usb: get CAN clock frequency from device Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 03/19] HID: holtek: fix mouse probing Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 04/19] IB/qib: Fix memory leak in qib_user_sdma_queue_pkts() Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 05/19] qlcnic: potential dereference null pointer of rx_queue->page_ring Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 06/19] bonding: fix ad_actor_system option setting to default Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 07/19] fjes: Check for error irq Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 08/19] drivers: net: smc911x: " Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 09/19] hwmon: (lm90) Fix usage of CONFIG2 register in detect function Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 10/19] ALSA: jack: Check the return value of kstrdup() Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 11/19] ALSA: drivers: opl3: Fix incorrect use of vp->state Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 12/19] x86/pkey: Fix undefined behaviour with PKRU_WD_BIT Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 13/19] ARM: 9169/1: entry: fix Thumb2 bug in iWMMXt exception handling Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 14/19] Input: i8042 - enable deferred probe quirk for ASUS UM325UA Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 15/19] hwmon: (lm90) Do not report busy status bit as alarm Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 16/19] ax25: NPD bug when detaching AX25 device Greg Kroah-Hartman
2021-12-27 15:27 ` Greg Kroah-Hartman [this message]
2021-12-27 15:27 ` [PATCH 4.9 18/19] hamradio: improve the incomplete fix to avoid NPD Greg Kroah-Hartman
2021-12-27 15:27 ` [PATCH 4.9 19/19] phonet/pep: refuse to enable an unbound pipe Greg Kroah-Hartman
2021-12-27 17:26 ` [PATCH 4.9 00/19] 4.9.295-rc1 review Florian Fainelli
2021-12-28 17:05 ` Guenter Roeck
2021-12-28 17:12 ` Naresh Kamboju
2021-12-28 21:30 ` Shuah Khan
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