linux-kernel - Re: [PATCH v2] remoteproc: sysfs/debugfs: fix race while updating recovery flag

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Message-ID: <22bcf613-5c0f-3043-f8ad-41bf45c5dc07@quicinc.com>
Date:   Wed, 1 Feb 2023 17:35:35 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     Satya Durga Srinivasu Prabhala <quic_satyap@...cinc.com>,
        <andersson@...nel.org>, <mathieu.poirier@...aro.org>
CC:     <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v2] remoteproc: sysfs/debugfs: fix race while updating
 recovery flag



On 2/1/2023 11:16 AM, Satya Durga Srinivasu Prabhala wrote:
> When multiple clients try to update the recovery flag, it is
> possible that, race condition would lead to undesired results
> as updates to recovery flag isn't protected by any mechanism
> today. To avoid such issues, take remoteproc mutex lock before
> updating recovery flag and release the lock once done.
> 
> Signed-off-by: Satya Durga Srinivasu Prabhala <quic_satyap@...cinc.com>

LGTM.

Reviewed-by: Mukesh Ojha <quic_mojha@...cinc.com>

-Mukesh
> ---
> v1 -> v2:
> - addressed comments from Mukesh Ojha
>    1. take & release lock only while updating recovery flag
>    2. update debugfs
> 
>   drivers/remoteproc/remoteproc_debugfs.c | 4 ++++
>   drivers/remoteproc/remoteproc_sysfs.c   | 4 ++++
>   2 files changed, 8 insertions(+)
> 
> diff --git a/drivers/remoteproc/remoteproc_debugfs.c b/drivers/remoteproc/remoteproc_debugfs.c
> index b86c1d09c70c..2c44d375024e 100644
> --- a/drivers/remoteproc/remoteproc_debugfs.c
> +++ b/drivers/remoteproc/remoteproc_debugfs.c
> @@ -226,10 +226,14 @@ rproc_recovery_write(struct file *filp, const char __user *user_buf,
>   
>   	if (!strncmp(buf, "enabled", count)) {
>   		/* change the flag and begin the recovery process if needed */
> +		mutex_lock(&rproc->lock);
>   		rproc->recovery_disabled = false;
> +		mutex_unlock(&rproc->lock);
>   		rproc_trigger_recovery(rproc);
>   	} else if (!strncmp(buf, "disabled", count)) {
> +		mutex_lock(&rproc->lock);
>   		rproc->recovery_disabled = true;
> +		mutex_unlock(&rproc->lock);
>   	} else if (!strncmp(buf, "recover", count)) {
>   		/* begin the recovery process without changing the flag */
>   		rproc_trigger_recovery(rproc);
> diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
> index 8c7ea8922638..628e0de9a132 100644
> --- a/drivers/remoteproc/remoteproc_sysfs.c
> +++ b/drivers/remoteproc/remoteproc_sysfs.c
> @@ -50,10 +50,14 @@ static ssize_t recovery_store(struct device *dev,
>   
>   	if (sysfs_streq(buf, "enabled")) {
>   		/* change the flag and begin the recovery process if needed */
> +		mutex_lock(&rproc->lock);
>   		rproc->recovery_disabled = false;
> +		mutex_unlock(&rproc->lock);
>   		rproc_trigger_recovery(rproc);
>   	} else if (sysfs_streq(buf, "disabled")) {
> +		mutex_lock(&rproc->lock);
>   		rproc->recovery_disabled = true;
> +		mutex_unlock(&rproc->lock);
>   	} else if (sysfs_streq(buf, "recover")) {
>   		/* begin the recovery process without changing the flag */
>   		rproc_trigger_recovery(rproc);