[PATCH v4 08/19] jobs: add job lock in find_* functions

[Emanuele Giuseppe Esposito <eesposit@redhat.com>]

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 | 14 +++++++++++++-
 job-qmp.c  | 13 ++++++++++++-
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 2e522dd7fe..7a9e9b4a13 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3311,7 +3311,10 @@ out:
     aio_context_release(aio_context);
 }
 
-/* Get a block job using its ID and acquire its AioContext */
+/*
+ * Get a block job using its ID and acquire its AioContext.
+ * Returns with job_lock held on success.
+ */
 static BlockJob *find_block_job(const char *id, AioContext **aio_context,
                                 Error **errp)
 {
@@ -3320,12 +3323,14 @@ 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;
     }
 
@@ -3346,6 +3351,7 @@ 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,
@@ -3372,6 +3378,7 @@ 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)
@@ -3386,6 +3393,7 @@ 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)
@@ -3400,6 +3408,7 @@ 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)
@@ -3414,6 +3423,7 @@ 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)
@@ -3437,6 +3447,7 @@ void qmp_block_job_finalize(const char *id, Error **errp)
     aio_context = block_job_get_aio_context(job);
     job_unref(&job->job);
     aio_context_release(aio_context);
+    job_unlock();
 }
 
 void qmp_block_job_dismiss(const char *id, Error **errp)
@@ -3453,6 +3464,7 @@ 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 06f970f6cf..a08cd7dd36 100644
--- a/job-qmp.c
+++ b/job-qmp.c
@@ -29,16 +29,21 @@
 #include "qapi/error.h"
 #include "trace/trace-root.h"
 
-/* Get a job using its ID and acquire its AioContext */
+/*
+ * Get a block job using its ID and acquire its AioContext.
+ * Returns with job_lock held on success.
+ */
 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 +65,7 @@ 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 +80,7 @@ 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 +95,7 @@ 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 +110,7 @@ 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 +134,7 @@ 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 +149,7 @@ 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)
-- 
2.31.1