linux-kernel - Re: [PATCH net,v3] net: hams: Fix deadlock caused by unsafe-irq lock in sp

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Message-ID: <20240419200453.13301f29@kernel.org>
Date: Fri, 19 Apr 2024 20:04:53 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Jeongjun Park <aha310510@...il.com>
Cc: syzbot+8e03da5d64bc85098811@...kaller.appspotmail.com,
 ajk@...nets.uni-bremen.de, davem@...emloft.net, edumazet@...gle.com,
 linux-hams@...r.kernel.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH net,v3] net: hams: Fix deadlock caused by unsafe-irq
 lock in sp_get()

On Sat, 20 Apr 2024 04:14:38 +0900 Jeongjun Park wrote:
> read_lock() present in sp_get() is interrupt-vulnerable, so the function needs to be modified.

I was going to make the same comments as on the other submission 
but then I realized this doesn't even build.

Please don't spam the list with completely untested code. You can
submit patches to syzbot for testing without CCing the list
or developers.

> Reported-by: syzbot+8e03da5d64bc85098811@...kaller.appspotmail.com
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Jeongjun Park <aha310510@...il.com>
> ---
>  drivers/net/hamradio/6pack.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
> index 6ed38a3cdd73..fee583b1e59a 100644
> --- a/drivers/net/hamradio/6pack.c
> +++ b/drivers/net/hamradio/6pack.c
> @@ -373,11 +373,11 @@ static struct sixpack *sp_get(struct tty_struct *tty)
>  {
>  	struct sixpack *sp;
>  
> -	read_lock(&disc_data_lock);
> +	read_lock_irq(&disc_data_lock);
>  	sp = tty->disc_data;
>  	if (sp)
>  		refcount_inc(&sp->refcnt);
> -	read_unlock(&disc_data_lock);
> +	read_unlock_irq(&disc_data_lock);
>  
>  	return sp;
>  }