netdev - Re: [PATCH net-next V2] ptp: fix corrupted list in ptp

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Date: Wed, 1 Nov 2023 17:12:53 -0700
From: Richard Cochran <richardcochran@...il.com>
To: Edward Adam Davis <eadavis@...com>
Cc: davem@...emloft.net, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, reibax@...il.com,
	syzbot+df3f3ef31f60781fa911@...kaller.appspotmail.com,
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH net-next V2] ptp: fix corrupted list in ptp_open

On Tue, Oct 31, 2023 at 05:07:08AM +0800, Edward Adam Davis wrote:
> There is no lock protection when writing ptp->tsevqs in ptp_open(),
> ptp_release(), which can cause data corruption,

Really?  How?

> use mutex lock to avoid this 
> issue.
> 
> Moreover, ptp_release() should not be used to release the queue in ptp_read(),
> and it should be deleted together.
> 
> Reported-and-tested-by: syzbot+df3f3ef31f60781fa911@...kaller.appspotmail.com
> Fixes: 8f5de6fb2453 ("ptp: support multiple timestamp event readers")
> Signed-off-by: Edward Adam Davis <eadavis@...com>
> ---
>  drivers/ptp/ptp_chardev.c | 11 +++++++++--
>  drivers/ptp/ptp_clock.c   |  3 +++
>  drivers/ptp/ptp_private.h |  1 +
>  3 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
> index 282cd7d24077..e31551d2697d 100644
> --- a/drivers/ptp/ptp_chardev.c
> +++ b/drivers/ptp/ptp_chardev.c
> @@ -109,6 +109,9 @@ int ptp_open(struct posix_clock_context *pccontext, fmode_t fmode)
>  	struct timestamp_event_queue *queue;
>  	char debugfsname[32];
>  
> +	if (mutex_lock_interruptible(&ptp->tsevq_mux)) 
> +		return -ERESTARTSYS;
> +

This mutex is not needed.

Please don't ignore review comments.

Thanks,
Richard