netdev - Re: [PATCH] iwlwifi: iwl-dbg: Use del_timer

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Date:   Wed, 13 Apr 2022 17:06:26 +0200
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     "Greenman, Gregory" <gregory.greenman@...el.com>
Cc:     "kvalo@...nel.org" <kvalo@...nel.org>,
        "linux@...ck-us.net" <linux@...ck-us.net>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "Berg, Johannes" <johannes.berg@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Coelho, Luciano" <luciano.coelho@...el.com>
Subject: Re: [PATCH] iwlwifi: iwl-dbg: Use del_timer_sync() before freeing

On Wed, Apr 13, 2022 at 11:56 AM Greenman, Gregory
<gregory.greenman@...el.com> wrote:
>
>
> 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@...dmis.org>
> > Cc: Steven Rostedt <rostedt@...dmis.org>
> > Cc: Johannes Berg <johannes.berg@...el.com>
> > Cc: Gregory Greenman <gregory.greenman@...el.com>
> > Fixes: 60e8abd9d3e91 ("iwlwifi: dbg_ini: add periodic trigger new API
> > support")
> > Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> > ---
> > 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@...el.com>

I have tested this on top of Linux v5.17.3-rc1.

Feel free to add my...

Tested-by: Sedat Dilek <sedat.dilek@...il.com> # Linux v5.17.3-rc1 and
Debian LLVM-14

- Sedat -