This is a note to let you know that I've just added the patch titled
hamradio: defer 6pack kfree after unregister_netdev
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
hamradio-defer-6pack-kfree-after-unregister_netdev.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0b9111922b1f399aba6ed1e1b8f2079c3da1aed8 Mon Sep 17 00:00:00 2001
From: Lin Ma <linma@xxxxxxxxxx>
Date: Mon, 8 Nov 2021 18:37:59 +0800
Subject: hamradio: defer 6pack kfree after unregister_netdev
From: Lin Ma <linma@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ovidiu Panait <ovidiu.panait@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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. */
Patches currently in stable-queue which might be from linma@xxxxxxxxxx are
queue-4.19/hamradio-remove-needs_free_netdev-to-avoid-uaf.patch
queue-4.19/hamradio-defer-6pack-kfree-after-unregister_netdev.patch
