From: Greg KH <gregkh@linuxfoundation.org>
To: Pavel Skripkin <paskripkin@gmail.com>
Cc: brookebasile@gmail.com, ath9k-devel@qca.qualcomm.com,
davem@davemloft.net, kuba@kernel.org, kvalo@codeaurora.org,
linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org,
syzbot+89bd486af9427a9fc605@syzkaller.appspotmail.com,
syzkaller-bugs@googlegroups.com
Subject: Re: Memory leak in ath9k_hif_usb_dealloc_tx_urbs()
Date: Wed, 31 Mar 2021 08:28:15 +0200 [thread overview]
Message-ID: <YGQWf1lP4ZOUFiG5@kroah.com> (raw)
In-Reply-To: <20210330193652.10642-1-paskripkin@gmail.com>
On Tue, Mar 30, 2021 at 10:36:52PM +0300, Pavel Skripkin wrote:
> Hi!
>
> I did some debugging on this
> https://syzkaller.appspot.com/bug?id=3ea507fb3c47426497b52bd82b8ef0dd5b6cc7ee
> and, I believe, I recognized the problem. The problem appears in case of
> ath9k_htc_hw_init() fail. In case of this fail all tx_buf->urb krefs will be
> initialized to 1, but in free function:
>
> static void ath9k_hif_usb_dealloc_tx_urbs(struct hif_device_usb *hif_dev)
>
> ....
>
> static void ath9k_hif_usb_dealloc_tx_urbs(struct hif_device_usb *hif_dev)
> {
> ...
> list_for_each_entry_safe(tx_buf, tx_buf_tmp,
> &hif_dev->tx.tx_buf, list) {
> usb_get_urb(tx_buf->urb);
> ...
> usb_free_urb(tx_buf->urb);
> ...
> }
>
> Krefs are incremented and then decremented, that means urbs won't be freed.
> I found your patch and I can't properly understand why You added usb_get_urb(tx_buf->urb).
> Can You explain please, I believe this will help me or somebody to fix this ussue :)
I think almost everyone who has looked into this has given up due to the
mess of twisty-passages here with almost no real-world benefits for
unwinding them :)
Good luck!
greg k-h
next prev parent reply other threads:[~2021-03-31 6:29 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-11 7:14 [PATCH] wireless: ath9k: hif_usb: fix race condition between usb_get_urb() and usb_kill_anchored_urbs() Brooke Basile
2020-09-20 2:03 ` Brooke Basile
2020-09-21 13:05 ` Kalle Valo
[not found] ` <20200921130559.005D8C43382@smtp.codeaurora.org>
2020-09-21 23:04 ` Brooke Basile
2021-03-30 19:36 ` Memory leak in ath9k_hif_usb_dealloc_tx_urbs() Pavel Skripkin
2021-03-31 6:28 ` Greg KH [this message]
2021-04-27 11:35 ` Atul Gopinathan
2021-04-27 11:50 ` Greg KH
2021-04-27 12:04 ` Pavel Skripkin
2021-04-27 12:29 ` Pavel Skripkin
2021-04-27 13:01 ` Atul Gopinathan
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