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SubjectRe: [PATCH] scsi: shost->async_scan should be protected by mutex_lock
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shost->async_scan should be protected by mutex_lock, otherwise the check
of "called twice" won't work.

Signed-off-by: Ouyang Zhaowei <ouyangzhaowei@huawei.com>
---
drivers/scsi/scsi_scan.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index fd88dab..20d539b 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1722,9 +1722,10 @@ static struct async_scan_data
*scsi_prep_async_scan(struct Scsi_Host *shost)
if (strncmp(scsi_scan_type, "sync", 4) == 0)
return NULL;

+ mutex_lock(&shost->scan_mutex);
if (shost->async_scan) {
shost_printk(KERN_DEBUG, shost, "%s called twice\n",
__func__);
- return NULL;
+ goto unlock;
}

data = kmalloc(sizeof(*data), GFP_KERNEL);
@@ -1735,7 +1736,6 @@ static struct async_scan_data
*scsi_prep_async_scan(struct Scsi_Host *shost)
goto err;
init_completion(&data->prev_finished);

- mutex_lock(&shost->scan_mutex);
spin_lock_irqsave(shost->host_lock, flags);
shost->async_scan = 1;
spin_unlock_irqrestore(shost->host_lock, flags);
@@ -1751,6 +1751,8 @@ static struct async_scan_data
*scsi_prep_async_scan(struct Scsi_Host *shost)

err:
kfree(data);
+ unlock:
+ mutex_unlock(&shost->scan_mutex);
return NULL;
}

On 2017.9.11 9:44, Tyrel Datwyler wrote:
> On 09/07/2017 11:54 PM, Ouyangzhaowei (Charles) wrote:
>> shost->async_scan should be protected by mutex_lock, otherwise the check
>> of "called twice" won't work.
>>
>> Signed-off-by: Ouyang Zhaowei <ouyangzhaowei@huawei.com>
>> ---
>> drivers/scsi/scsi_scan.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
>> index fd88dab..1d1df51 100644
>> --- a/drivers/scsi/scsi_scan.c
>> +++ b/drivers/scsi/scsi_scan.c
>> @@ -1722,6 +1722,7 @@ static struct async_scan_data
>> *scsi_prep_async_scan(struct Scsi_Host *shost)
>> if (strncmp(scsi_scan_type, "sync", 4) == 0)
>> return NULL;
>>
>> + mutex_lock(&shost->scan_mutex);
>
> The mutex will not be unlocked in the event that either the host has called
> scsi_prep_async_scan() twice, or a condition is meet the branches to the "err" label prior
> to where the original mutex_lock() was located below.

Thanks for the review, I modified the patch, please check it out again.

>
> -Tyrel
>
>> if (shost->async_scan) {
>> shost_printk(KERN_DEBUG, shost, "%s called twice\n",
>> __func__);
>> return NULL;
>> @@ -1735,7 +1736,6 @@ static struct async_scan_data
>> *scsi_prep_async_scan(struct Scsi_Host *shost)
>> goto err;
>> init_completion(&data->prev_finished);
>>
>> - mutex_lock(&shost->scan_mutex);
>> spin_lock_irqsave(shost->host_lock, flags);
>> shost->async_scan = 1;
>> spin_unlock_irqrestore(shost->host_lock, flags);
>>
>
>
> .
>

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