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authorMarkus Armbruster <armbru@redhat.com>2018-06-14 21:14:30 +0200
committerKevin Wolf <kwolf@redhat.com>2018-06-15 14:49:44 +0200
commite5af0da1dcbfb1a4694150f9954554fb6df88819 (patch)
tree0c12475f20208df9d665632a667016cc12a1ebef /block/parallels.c
parent0bcc8e5bd8d6fd6e5cb6462054f7cfa45b282f9a (diff)
block: Fix -blockdev for certain non-string scalars
Configuration flows through the block subsystem in a rather peculiar way. Configuration made with -drive enters it as QemuOpts. Configuration made with -blockdev / blockdev-add enters it as QAPI type BlockdevOptions. The block subsystem uses QDict, QemuOpts and QAPI types internally. The precise flow is next to impossible to explain (I tried for this commit message, but gave up after wasting several hours). What I can explain is a flaw in the BlockDriver interface that leads to this bug: $ qemu-system-x86_64 -blockdev node-name=n1,driver=nfs,server.type=inet,server.host=localhost,path=/foo/bar,user=1234 qemu-system-x86_64: -blockdev node-name=n1,driver=nfs,server.type=inet,server.host=localhost,path=/foo/bar,user=1234: Internal error: parameter user invalid QMP blockdev-add is broken the same way. Here's what happens. The block layer passes configuration represented as flat QDict (with dotted keys) to BlockDriver methods .bdrv_file_open(). The QDict's members are typed according to the QAPI schema. nfs_file_open() converts it to QAPI type BlockdevOptionsNfs, with qdict_crumple() and a qobject input visitor. This visitor comes in two flavors. The plain flavor requires scalars to be typed according to the QAPI schema. That's the case here. The keyval flavor requires string scalars. That's not the case here. nfs_file_open() uses the latter, and promptly falls apart for members @user, @group, @tcp-syn-count, @readahead-size, @page-cache-size, @debug. Switching to the plain flavor would fix -blockdev, but break -drive, because there the scalars arrive in nfs_file_open() as strings. The proper fix would be to replace the QDict by QAPI type BlockdevOptions in the BlockDriver interface. Sadly, that's beyond my reach right now. Next best would be to fix the block layer to always pass correctly typed QDicts to the BlockDriver methods. Also beyond my reach. What I can do is throw another hack onto the pile: have nfs_file_open() convert all members to string, so use of the keyval flavor actually works, by replacing qdict_crumple() by new function qdict_crumple_for_keyval_qiv(). The pattern "pass result of qdict_crumple() to qobject_input_visitor_new_keyval()" occurs several times more: * qemu_rbd_open() Same issue as nfs_file_open(), but since BlockdevOptionsRbd has only string members, its only a latent bug. Fix it anyway. * parallels_co_create_opts(), qcow_co_create_opts(), qcow2_co_create_opts(), bdrv_qed_co_create_opts(), sd_co_create_opts(), vhdx_co_create_opts(), vpc_co_create_opts() These work, because they create the QDict with qemu_opts_to_qdict_filtered(), which creates only string scalars. The function sports a TODO comment asking for better typing; that's going to be fun. Use qdict_crumple_for_keyval_qiv() to be safe. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block/parallels.c')
-rw-r--r--block/parallels.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/block/parallels.c b/block/parallels.c
index c1d9643498..695899fc4b 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -653,7 +653,7 @@ static int coroutine_fn parallels_co_create_opts(const char *filename,
qdict_put_str(qdict, "driver", "parallels");
qdict_put_str(qdict, "file", bs->node_name);
- qobj = qdict_crumple(qdict, errp);
+ qobj = qdict_crumple_for_keyval_qiv(qdict, errp);
qobject_unref(qdict);
qdict = qobject_to(QDict, qobj);
if (qdict == NULL) {