[PATCH 1/2] rv: Fully convert enabled_monitors to use list_head as iterator

[PATCH 1/2] rv: Fully convert enabled_monitors to use list_head as iterator

[Nam Cao]

The callbacks in enabled_monitors_seq_ops are inconsistent. Some treat the
iterator as struct rv_monitor *, while others treat the iterator as struct
list_head *.

This causes a wrong type cast and crashes the system as reported by Nathan.

Convert everything to use struct list_head * as iterator. This also makes
enabled_monitors consistent with available_monitors.

Fixes: de090d1ccae1 ("rv: Fix wrong type cast in enabled_monitors_next()")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/linux-trace-kernel/20250923002004.GA2836051@ax162/
Signed-off-by: Nam Cao <namcao@linutronix.de>
Cc: <stable@vger.kernel.org>
---
 kernel/trace/rv/rv.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/rv/rv.c b/kernel/trace/rv/rv.c
index 48338520376f..43e9ea473cda 100644
--- a/kernel/trace/rv/rv.c
+++ b/kernel/trace/rv/rv.c
@@ -501,7 +501,7 @@ static void *enabled_monitors_next(struct seq_file *m, void *p, loff_t *pos)
 
 	list_for_each_entry_continue(mon, &rv_monitors_list, list) {
 		if (mon->enabled)
-			return mon;
+			return &mon->list;
 	}
 
 	return NULL;
@@ -509,7 +509,7 @@ static void *enabled_monitors_next(struct seq_file *m, void *p, loff_t *pos)
 
 static void *enabled_monitors_start(struct seq_file *m, loff_t *pos)
 {
-	struct rv_monitor *mon;
+	struct list_head *head;
 	loff_t l;
 
 	mutex_lock(&rv_interface_lock);
@@ -517,15 +517,15 @@ static void *enabled_monitors_start(struct seq_file *m, loff_t *pos)
 	if (list_empty(&rv_monitors_list))
 		return NULL;
 
-	mon = list_entry(&rv_monitors_list, struct rv_monitor, list);
+	head = &rv_monitors_list;
 
 	for (l = 0; l <= *pos; ) {
-		mon = enabled_monitors_next(m, mon, &l);
-		if (!mon)
+		head = enabled_monitors_next(m, head, &l);
+		if (!head)
 			break;
 	}
 
-	return mon;
+	return head;
 }
 
 /*
-- 
2.51.0

Re: [PATCH 1/2] rv: Fully convert enabled_monitors to use list_head as iterator

[Gabriele Monaco]

On Thu, 2025-10-02 at 08:22 +0000, Nam Cao wrote:
> The callbacks in enabled_monitors_seq_ops are inconsistent. Some treat the
> iterator as struct rv_monitor *, while others treat the iterator as struct
> list_head *.
> 
> This causes a wrong type cast and crashes the system as reported by Nathan.
> 
> Convert everything to use struct list_head * as iterator. This also makes
> enabled_monitors consistent with available_monitors.
> 

Looks good to me and passes my tests.

Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>

Thanks,
Gabriele

> Fixes: de090d1ccae1 ("rv: Fix wrong type cast in enabled_monitors_next()")
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Closes:
> https://lore.kernel.org/linux-trace-kernel/20250923002004.GA2836051@ax162/
> Signed-off-by: Nam Cao <namcao@linutronix.de>
> Cc: <stable@vger.kernel.org>
> ---
>  kernel/trace/rv/rv.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/trace/rv/rv.c b/kernel/trace/rv/rv.c
> index 48338520376f..43e9ea473cda 100644
> --- a/kernel/trace/rv/rv.c
> +++ b/kernel/trace/rv/rv.c
> @@ -501,7 +501,7 @@ static void *enabled_monitors_next(struct seq_file *m,
> void *p, loff_t *pos)
>  
>  	list_for_each_entry_continue(mon, &rv_monitors_list, list) {
>  		if (mon->enabled)
> -			return mon;
> +			return &mon->list;
>  	}
>  
>  	return NULL;
> @@ -509,7 +509,7 @@ static void *enabled_monitors_next(struct seq_file *m,
> void *p, loff_t *pos)
>  
>  static void *enabled_monitors_start(struct seq_file *m, loff_t *pos)
>  {
> -	struct rv_monitor *mon;
> +	struct list_head *head;
>  	loff_t l;
>  
>  	mutex_lock(&rv_interface_lock);
> @@ -517,15 +517,15 @@ static void *enabled_monitors_start(struct seq_file *m,
> loff_t *pos)
>  	if (list_empty(&rv_monitors_list))
>  		return NULL;
>  
> -	mon = list_entry(&rv_monitors_list, struct rv_monitor, list);
> +	head = &rv_monitors_list;
>  
>  	for (l = 0; l <= *pos; ) {
> -		mon = enabled_monitors_next(m, mon, &l);
> -		if (!mon)
> +		head = enabled_monitors_next(m, head, &l);
> +		if (!head)
>  			break;
>  	}
>  
> -	return mon;
> +	return head;
>  }
>  
>  /*