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[RFC PATCH v2 13/14] jobs: add job lock in find_* functions

Emanuele Giuseppe Esposito posted 14 patches 4 years, 3 months ago
Maintainers: Fam Zheng <fam@euphon.net>, Kevin Wolf <kwolf@redhat.com>, John Snow <jsnow@redhat.com>, Wen Congyang <wencongyang2@huawei.com>, Hanna Reitz <hreitz@redhat.com>, Markus Armbruster <armbru@redhat.com>, Xie Changlong <xiechanglong.d@gmail.com>, Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>, Stefan Hajnoczi <stefanha@redhat.com>
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[RFC PATCH v2 13/14] jobs: add job lock in find_* functions
Posted by Emanuele Giuseppe Esposito 4 years, 3 months ago 
Both blockdev.c and job-qmp.c have TOC/TOU conditions, because
they first search for the job and then perform an action on it.
Therefore, we need to do the search + action under the same
job mutex critical section.

Note: at this stage, job_{lock/unlock} and job lock guard macros
are *nop*.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 blockdev.c | 9 +++++++++
 job-qmp.c  | 8 ++++++++
 2 files changed, 17 insertions(+)

diff --git a/blockdev.c b/blockdev.c
index c5a835d9ed..0bd79757fc 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3327,12 +3327,14 @@ static BlockJob *find_block_job(const char *id, AioContext **aio_context,
     assert(id != NULL);
 
     *aio_context = NULL;
+    job_lock();
 
     job = block_job_get(id);
 
     if (!job) {
         error_set(errp, ERROR_CLASS_DEVICE_NOT_ACTIVE,
                   "Block job '%s' not found", id);
+        job_unlock();
         return NULL;
     }
 
@@ -3353,6 +3355,7 @@ void qmp_block_job_set_speed(const char *device, int64_t speed, Error **errp)
 
     block_job_set_speed(job, speed, errp);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_block_job_cancel(const char *device,
@@ -3379,6 +3382,7 @@ void qmp_block_job_cancel(const char *device,
     job_user_cancel(&job->job, force, errp);
 out:
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_block_job_pause(const char *device, Error **errp)
@@ -3393,6 +3397,7 @@ void qmp_block_job_pause(const char *device, Error **errp)
     trace_qmp_block_job_pause(job);
     job_user_pause(&job->job, errp);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_block_job_resume(const char *device, Error **errp)
@@ -3407,6 +3412,7 @@ void qmp_block_job_resume(const char *device, Error **errp)
     trace_qmp_block_job_resume(job);
     job_user_resume(&job->job, errp);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_block_job_complete(const char *device, Error **errp)
@@ -3421,6 +3427,7 @@ void qmp_block_job_complete(const char *device, Error **errp)
     trace_qmp_block_job_complete(job);
     job_complete(&job->job, errp);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_block_job_finalize(const char *id, Error **errp)
@@ -3444,6 +3451,7 @@ void qmp_block_job_finalize(const char *id, Error **errp)
     aio_context = blk_get_aio_context(job->blk);
     job_unref(&job->job);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_block_job_dismiss(const char *id, Error **errp)
@@ -3460,6 +3468,7 @@ void qmp_block_job_dismiss(const char *id, Error **errp)
     job = &bjob->job;
     job_dismiss(&job, errp);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_change_backing_file(const char *device,
diff --git a/job-qmp.c b/job-qmp.c
index a355dc2954..8f07c51db8 100644
--- a/job-qmp.c
+++ b/job-qmp.c
@@ -35,10 +35,12 @@ static Job *find_job(const char *id, AioContext **aio_context, Error **errp)
     Job *job;
 
     *aio_context = NULL;
+    job_lock();
 
     job = job_get(id);
     if (!job) {
         error_setg(errp, "Job not found");
+        job_unlock();
         return NULL;
     }
 
@@ -60,6 +62,7 @@ void qmp_job_cancel(const char *id, Error **errp)
     trace_qmp_job_cancel(job);
     job_user_cancel(job, true, errp);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_job_pause(const char *id, Error **errp)
@@ -74,6 +77,7 @@ void qmp_job_pause(const char *id, Error **errp)
     trace_qmp_job_pause(job);
     job_user_pause(job, errp);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_job_resume(const char *id, Error **errp)
@@ -88,6 +92,7 @@ void qmp_job_resume(const char *id, Error **errp)
     trace_qmp_job_resume(job);
     job_user_resume(job, errp);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_job_complete(const char *id, Error **errp)
@@ -102,6 +107,7 @@ void qmp_job_complete(const char *id, Error **errp)
     trace_qmp_job_complete(job);
     job_complete(job, errp);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_job_finalize(const char *id, Error **errp)
@@ -125,6 +131,7 @@ void qmp_job_finalize(const char *id, Error **errp)
     aio_context = job->aio_context;
     job_unref(job);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_job_dismiss(const char *id, Error **errp)
@@ -139,6 +146,7 @@ void qmp_job_dismiss(const char *id, Error **errp)
     trace_qmp_job_dismiss(job);
     job_dismiss(&job, errp);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 static JobInfo *job_query_single(Job *job, Error **errp)
-- 
2.27.0
Re: [RFC PATCH v2 13/14] jobs: add job lock in find_* functions
Posted by Vladimir Sementsov-Ogievskiy 4 years, 1 month ago 
04.11.2021 17:53, Emanuele Giuseppe Esposito wrote:
> Both blockdev.c and job-qmp.c have TOC/TOU conditions, because
> they first search for the job and then perform an action on it.
> Therefore, we need to do the search + action under the same
> job mutex critical section.
> 
> Note: at this stage, job_{lock/unlock} and job lock guard macros
> are *nop*.
> 
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> ---
>   blockdev.c | 9 +++++++++
>   job-qmp.c  | 8 ++++++++
>   2 files changed, 17 insertions(+)
> 
> diff --git a/blockdev.c b/blockdev.c
> index c5a835d9ed..0bd79757fc 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -3327,12 +3327,14 @@ static BlockJob *find_block_job(const char *id, AioContext **aio_context,
>       assert(id != NULL);
>   
>       *aio_context = NULL;
> +    job_lock();

JOB_LOCK_GUARD() will look better in this case

>   
>       job = block_job_get(id);
>   
>       if (!job) {
>           error_set(errp, ERROR_CLASS_DEVICE_NOT_ACTIVE,
>                     "Block job '%s' not found", id);
> +        job_unlock();
>           return NULL;
>       }
>   
> @@ -3353,6 +3355,7 @@ void qmp_block_job_set_speed(const char *device, int64_t speed, Error **errp)
>   
>       block_job_set_speed(job, speed, errp);
>       aio_context_release(aio_context);
> +    job_unlock();

You add job_unlock(), but not job_lock() ? Something is wrong. And anyway, I thin JOB_LOCK_GUARD / WITH_JOB_LOCK_GUARD are generally safer

>   }
>   
>   void qmp_block_job_cancel(const char *device,
> @@ -3379,6 +3382,7 @@ void qmp_block_job_cancel(const char *device,
>       job_user_cancel(&job->job, force, errp);
>   out:
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_block_job_pause(const char *device, Error **errp)
> @@ -3393,6 +3397,7 @@ void qmp_block_job_pause(const char *device, Error **errp)
>       trace_qmp_block_job_pause(job);
>       job_user_pause(&job->job, errp);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_block_job_resume(const char *device, Error **errp)
> @@ -3407,6 +3412,7 @@ void qmp_block_job_resume(const char *device, Error **errp)
>       trace_qmp_block_job_resume(job);
>       job_user_resume(&job->job, errp);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_block_job_complete(const char *device, Error **errp)
> @@ -3421,6 +3427,7 @@ void qmp_block_job_complete(const char *device, Error **errp)
>       trace_qmp_block_job_complete(job);
>       job_complete(&job->job, errp);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_block_job_finalize(const char *id, Error **errp)
> @@ -3444,6 +3451,7 @@ void qmp_block_job_finalize(const char *id, Error **errp)
>       aio_context = blk_get_aio_context(job->blk);
>       job_unref(&job->job);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_block_job_dismiss(const char *id, Error **errp)
> @@ -3460,6 +3468,7 @@ void qmp_block_job_dismiss(const char *id, Error **errp)
>       job = &bjob->job;
>       job_dismiss(&job, errp);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_change_backing_file(const char *device,
> diff --git a/job-qmp.c b/job-qmp.c
> index a355dc2954..8f07c51db8 100644
> --- a/job-qmp.c
> +++ b/job-qmp.c
> @@ -35,10 +35,12 @@ static Job *find_job(const char *id, AioContext **aio_context, Error **errp)
>       Job *job;
>   
>       *aio_context = NULL;
> +    job_lock();
>   
>       job = job_get(id);
>       if (!job) {
>           error_setg(errp, "Job not found");
> +        job_unlock();
>           return NULL;
>       }
>   
> @@ -60,6 +62,7 @@ void qmp_job_cancel(const char *id, Error **errp)
>       trace_qmp_job_cancel(job);
>       job_user_cancel(job, true, errp);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_job_pause(const char *id, Error **errp)
> @@ -74,6 +77,7 @@ void qmp_job_pause(const char *id, Error **errp)
>       trace_qmp_job_pause(job);
>       job_user_pause(job, errp);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_job_resume(const char *id, Error **errp)
> @@ -88,6 +92,7 @@ void qmp_job_resume(const char *id, Error **errp)
>       trace_qmp_job_resume(job);
>       job_user_resume(job, errp);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_job_complete(const char *id, Error **errp)
> @@ -102,6 +107,7 @@ void qmp_job_complete(const char *id, Error **errp)
>       trace_qmp_job_complete(job);
>       job_complete(job, errp);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_job_finalize(const char *id, Error **errp)
> @@ -125,6 +131,7 @@ void qmp_job_finalize(const char *id, Error **errp)
>       aio_context = job->aio_context;
>       job_unref(job);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   void qmp_job_dismiss(const char *id, Error **errp)
> @@ -139,6 +146,7 @@ void qmp_job_dismiss(const char *id, Error **errp)
>       trace_qmp_job_dismiss(job);
>       job_dismiss(&job, errp);
>       aio_context_release(aio_context);
> +    job_unlock();
>   }
>   
>   static JobInfo *job_query_single(Job *job, Error **errp)
> 


-- 
Best regards,
Vladimir
Re: [RFC PATCH v2 13/14] jobs: add job lock in find_* functions
Posted by Vladimir Sementsov-Ogievskiy 4 years, 1 month ago 
18.12.2021 15:11, Vladimir Sementsov-Ogievskiy wrote:
> 04.11.2021 17:53, Emanuele Giuseppe Esposito wrote:
>> Both blockdev.c and job-qmp.c have TOC/TOU conditions, because
>> they first search for the job and then perform an action on it.
>> Therefore, we need to do the search + action under the same
>> job mutex critical section.
>>
>> Note: at this stage, job_{lock/unlock} and job lock guard macros
>> are *nop*.
>>
>> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
>> ---
>>   blockdev.c | 9 +++++++++
>>   job-qmp.c  | 8 ++++++++
>>   2 files changed, 17 insertions(+)
>>
>> diff --git a/blockdev.c b/blockdev.c
>> index c5a835d9ed..0bd79757fc 100644
>> --- a/blockdev.c
>> +++ b/blockdev.c
>> @@ -3327,12 +3327,14 @@ static BlockJob *find_block_job(const char *id, AioContext **aio_context,
>>       assert(id != NULL);
>>       *aio_context = NULL;
>> +    job_lock();
> 
> JOB_LOCK_GUARD() will look better in this case
> 
>>       job = block_job_get(id);
>>       if (!job) {
>>           error_set(errp, ERROR_CLASS_DEVICE_NOT_ACTIVE,
>>                     "Block job '%s' not found", id);
>> +        job_unlock();
>>           return NULL;
>>       }
>> @@ -3353,6 +3355,7 @@ void qmp_block_job_set_speed(const char *device, int64_t speed, Error **errp)
>>       block_job_set_speed(job, speed, errp);
>>       aio_context_release(aio_context);
>> +    job_unlock();
> 
> You add job_unlock(), but not job_lock() ? Something is wrong. And anyway, I thin JOB_LOCK_GUARD / WITH_JOB_LOCK_GUARD are generally safer

Ah, I understand now what's going on. If comment "Returns with job_lock held on success" appear in this patch, it would be more obvious.

-- 
Best regards,
Vladimir

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