Re: [PATCH] iwlwifi: iwl-dbg: Use del_timer_sync() before freeing

[Greenman, Gregory]

On Mon, 2022-04-11 at 08:42 -0700, Guenter Roeck wrote:
> In Chrome OS, a large number of crashes is observed due to corrupted
> timer
> lists. Steven Rostedt pointed out that this usually happens when a
> timer
> is freed while still active, and that the problem is often triggered
> by code calling del_timer() instead of del_timer_sync() just before
> freeing.
> 
> Steven also identified the iwlwifi driver as one of the possible
> culprits
> since it does exactly that.
> 
> Reported-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Johannes Berg <johannes.berg@xxxxxxxxx>
> Cc: Gregory Greenman <gregory.greenman@xxxxxxxxx>
> Fixes: 60e8abd9d3e91 ("iwlwifi: dbg_ini: add periodic trigger new API
> support")
> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
> v1 (from RFC):
>     Removed Shahar S Matityahu from Cc: and added Gregory Greenman.
>     No functional change.
> 
> I thought about the need to add a mutex to protect the timer list,
> but
> I convinced myself that it is not necessary because the code adding
> the timer list and the code removing it should never be never
> executed
> in parallel.
> 
>  drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c
> b/drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c
> index 866a33f49915..3237d4b528b5 100644
> --- a/drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c
> +++ b/drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c
> @@ -371,7 +371,7 @@ void iwl_dbg_tlv_del_timers(struct iwl_trans
> *trans)
>         struct iwl_dbg_tlv_timer_node *node, *tmp;
>  
>         list_for_each_entry_safe(node, tmp, timer_list, list) {
> -               del_timer(&node->timer);
> +               del_timer_sync(&node->timer);
>                 list_del(&node->list);
>                 kfree(node);
>         }

Hi Kalle,

Can you please pick it up to wireless-drivers for the next rc?
It is an important fix.
Luca has already assigned it to you in patchwork.

Thanks!

Acked-by: Gregory Greenman <gregory.greenman@xxxxxxxxx>