linux-kernel - Re: [PATCH] scsi: fix missing lock protection

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Message-ID: <03b1b927-fb33-46e8-b38d-08e986f45672@acm.org>
Date: Wed, 19 Feb 2025 10:06:07 -0800
From: Bart Van Assche <bvanassche@....org>
To: Chaohai Chen <wdhh66@....com>, martin.petersen@...cle.com
Cc: James.Bottomley@...senPartnership.com, linux-scsi@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: fix missing lock protection

On 2/19/25 12:11 AM, Chaohai Chen wrote:
> async_scan_lock is designed to protect the scanning_hosts list,
> but there is no protection here.
> 
> Signed-off-by: Chaohai Chen <wdhh66@....com>
> ---
>   drivers/scsi/scsi_scan.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index 087fcbfc9aaa..9a90e6ba5603 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -151,8 +151,12 @@ int scsi_complete_async_scans(void)
>   	struct async_scan_data *data;
>   
>   	do {
> -		if (list_empty(&scanning_hosts))
> +		spin_lock(&async_scan_lock);
> +		if (list_empty(&scanning_hosts)) {
> +			spin_unlock(&async_scan_lock);
>   			return 0;
> +		}
> +		spin_unlock(&async_scan_lock);
>   		/* If we can't get memory immediately, that's OK.  Just
>   		 * sleep a little.  Even if we never get memory, the async
>   		 * scans will finish eventually.

Has it been considered to use scoped_guard() as in the untested patch
below?

Thanks,

Bart.


diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 087fcbfc9aaa..efc90571ab47 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -151,8 +151,9 @@ int scsi_complete_async_scans(void)
  	struct async_scan_data *data;

  	do {
-		if (list_empty(&scanning_hosts))
-			return 0;
+		scoped_guard(spinlock, &async_scan_lock)
+			if (list_empty(&scanning_hosts))
+				return 0;
  		/* If we can't get memory immediately, that's OK.  Just
  		 * sleep a little.  Even if we never get memory, the async
  		 * scans will finish eventually.