crypto: perform permission checks under BQL

Move the permission API calls into driver-specific callbacks
that always run under BQL. In this case, bdrv_crypto_luks
needs to perform permission checks before and after
qcrypto_block_amend_options(). The problem is that the caller,
block_crypto_amend_options_generic_luks(), can also run in I/O
from .bdrv_co_amend(). This does not comply with Global State-I/O API split,
as permissions API must always run under BQL.

Firstly, introduce .bdrv_amend_pre_run() and .bdrv_amend_clean()
callbacks. These two callbacks are guaranteed to be invoked under
BQL, respectively before and after .bdrv_co_amend().
They take care of performing the permission checks
in the same way as they are currently done before and after
qcrypto_block_amend_options().
These callbacks are in preparation for next patch, where we
delete the original permission check. Right now they just add redundant
control.

Then, call .bdrv_amend_pre_run() before job_start in
qmp_x_blockdev_amend(), so that it will be run before the job coroutine
is created and stay in the main loop.
As a cleanup, use JobDriver's .clean() callback to call
.bdrv_amend_clean(), and run amend-specific cleanup callbacks under BQL.

After this patch, permission failures occur early in the blockdev-amend
job to update a LUKS volume's keys.  iotest 296 must now expect them in
x-blockdev-amend's QMP reply instead of waiting for the actual job to
fail later.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220209105452.1694545-2-eesposit@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220304153729.711387-6-hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/block/amend.c b/block/amend.c
index 392df9ef83..f465738665 100644
--- a/block/amend.c
+++ b/block/amend.c
@@ -53,10 +53,29 @@ static int coroutine_fn blockdev_amend_run(Job *job, Error **errp)
     return ret;
 }
 
+static int blockdev_amend_pre_run(BlockdevAmendJob *s, Error **errp)
+{
+    if (s->bs->drv->bdrv_amend_pre_run) {
+        return s->bs->drv->bdrv_amend_pre_run(s->bs, errp);
+    }
+
+    return 0;
+}
+
+static void blockdev_amend_clean(Job *job)
+{
+    BlockdevAmendJob *s = container_of(job, BlockdevAmendJob, common);
+
+    if (s->bs->drv->bdrv_amend_clean) {
+        s->bs->drv->bdrv_amend_clean(s->bs);
+    }
+}
+
 static const JobDriver blockdev_amend_job_driver = {
     .instance_size = sizeof(BlockdevAmendJob),
     .job_type      = JOB_TYPE_AMEND,
     .run           = blockdev_amend_run,
+    .clean         = blockdev_amend_clean,
 };
 
 void qmp_x_blockdev_amend(const char *job_id,
@@ -113,5 +132,11 @@ void qmp_x_blockdev_amend(const char *job_id,
     s->bs = bs,
     s->opts = QAPI_CLONE(BlockdevAmendOptions, options),
     s->force = has_force ? force : false;
+
+    if (blockdev_amend_pre_run(s, errp)) {
+        job_early_fail(&s->common);
+        return;
+    }
+
     job_start(&s->common);
 }