hams: Fix deadlock caused by unsafe-irq lock in sp_get()

[PATCH] hams: Fix deadlock caused by unsafe-irq lock in sp_get()

Posted by Jeongjun Park 1 year, 10 months ago


read_lock() present in sp_get() is interrupt-vulnerable, so the function needs to be modified.


Reported-by: syzbot+8e03da5d64bc85098811@syzkaller.appspotmail.com
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
---
 drivers/net/hamradio/6pack.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index 6ed38a3cdd73..f882682ff0c8 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c
@@ -372,12 +372,13 @@ static DEFINE_RWLOCK(disc_data_lock);
 static struct sixpack *sp_get(struct tty_struct *tty)
 {
 	struct sixpack *sp;
+	unsigned long flags;
 
-	read_lock(&disc_data_lock);
+	flags = read_lock_irqsave(&disc_data_lock);
 	sp = tty->disc_data;
 	if (sp)
 		refcount_inc(&sp->refcnt);
-	read_unlock(&disc_data_lock);
+	read_unlock_irqrestore(&disc_data_lock, flags);
 
 	return sp;
 }
-- 
2.34.1

Re: [PATCH] hams: Fix deadlock caused by unsafe-irq lock in sp_get()

Posted by Dan Carpenter 1 year, 9 months ago

On Fri, Apr 19, 2024 at 02:30:37AM +0900, Jeongjun Park wrote:
> 
> read_lock() present in sp_get() is interrupt-vulnerable, so the function needs to be modified.
> 
> 
> Reported-by: syzbot+8e03da5d64bc85098811@syzkaller.appspotmail.com
> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> ---
>  drivers/net/hamradio/6pack.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
> index 6ed38a3cdd73..f882682ff0c8 100644
> --- a/drivers/net/hamradio/6pack.c
> +++ b/drivers/net/hamradio/6pack.c
> @@ -372,12 +372,13 @@ static DEFINE_RWLOCK(disc_data_lock);
>  static struct sixpack *sp_get(struct tty_struct *tty)
>  {
>  	struct sixpack *sp;
> +	unsigned long flags;
>  
> -	read_lock(&disc_data_lock);
> +	flags = read_lock_irqsave(&disc_data_lock);

This doesn't compile.  At least build test your patches.

regards,
dan carpenter