block: Parse filenames only when explicitly requested

When handling image filenames from legacy options such as -drive or from
tools, these filenames are parsed for protocol prefixes, including for
the json:{} pseudo-protocol.

This behaviour is intended for filenames that come directly from the
command line and for backing files, which may come from the image file
itself. Higher level management tools generally take care to verify that
untrusted images don't contain a bad (or any) backing file reference;
'qemu-img info' is a suitable tool for this.

However, for other files that can be referenced in images, such as
qcow2 data files or VMDK extents, the string from the image file is
usually not verified by management tools - and 'qemu-img info' wouldn't
be suitable because in contrast to backing files, it already opens these
other referenced files. So here the string should be interpreted as a
literal local filename. More complex configurations need to be specified
explicitly on the command line or in QMP.

This patch changes bdrv_open_inherit() so that it only parses filenames
if a new parameter parse_filename is true. It is set for the top level
in bdrv_open(), for the file child and for the backing file child. All
other callers pass false and disable filename parsing this way.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
(cherry picked from commit 7ead946998610657d38d1a505d5f25300d4ca613)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(Mjt: backport patch to 7.2, without:
  v8.0.0-2069-g8394c35ee148 "block: Fix AioContext locking in bdrv_open_child()"
  v8.1.0-801-gafdaeb9ea06e "block: Mark bdrv_attach_child() GRAPH_WRLOCK"
  v8.2.0-rc0-59-g6bc0bcc89f84 "block: Fix deadlocks in bdrv_graph_wrunlock()"
  v8.2.0-132-g6bc30f194985 "graph-lock: remove AioContext locking"
  v8.2.0-133-gb49f4755c7fa "block: remove AioContext locking")

1 files changed, 49 insertions, 27 deletions

diff --git a/block.c b/block.c
index a18f052374..ea369a3fe5 100644
--- a/block.c
+++ b/block.c
@@ -85,6 +85,7 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
                                            BlockDriverState *parent,
                                            const BdrvChildClass *child_class,
                                            BdrvChildRole child_role,
+                                           bool parse_filename,
                                            Error **errp);
 
 static bool bdrv_recurse_has_child(BlockDriverState *bs,
@@ -2051,7 +2052,8 @@ static void parse_json_protocol(QDict *options, const char **pfilename,
  * block driver has been specified explicitly.
  */
 static int bdrv_fill_options(QDict **options, const char *filename,
-                             int *flags, Error **errp)
+                             int *flags, bool allow_parse_filename,
+                             Error **errp)
 {
     const char *drvname;
     bool protocol = *flags & BDRV_O_PROTOCOL;
@@ -2093,7 +2095,7 @@ static int bdrv_fill_options(QDict **options, const char *filename,
     if (protocol && filename) {
         if (!qdict_haskey(*options, "filename")) {
             qdict_put_str(*options, "filename", filename);
-            parse_filename = true;
+            parse_filename = allow_parse_filename;
         } else {
             error_setg(errp, "Can't specify 'file' and 'filename' options at "
                              "the same time");
@@ -3516,7 +3518,8 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
     }
 
     backing_hd = bdrv_open_inherit(backing_filename, reference, options, 0, bs,
-                                   &child_of_bds, bdrv_backing_role(bs), errp);
+                                   &child_of_bds, bdrv_backing_role(bs), true,
+                                   errp);
     if (!backing_hd) {
         bs->open_flags |= BDRV_O_NO_BACKING;
         error_prepend(errp, "Could not open backing file: ");
@@ -3549,7 +3552,8 @@ free_exit:
 static BlockDriverState *
 bdrv_open_child_bs(const char *filename, QDict *options, const char *bdref_key,
                    BlockDriverState *parent, const BdrvChildClass *child_class,
-                   BdrvChildRole child_role, bool allow_none, Error **errp)
+                   BdrvChildRole child_role, bool allow_none,
+                   bool parse_filename, Error **errp)
 {
     BlockDriverState *bs = NULL;
     QDict *image_options;
@@ -3580,7 +3584,8 @@ bdrv_open_child_bs(const char *filename, QDict *options, const char *bdref_key,
     }
 
     bs = bdrv_open_inherit(filename, reference, image_options, 0,
-                           parent, child_class, child_role, errp);
+                           parent, child_class, child_role, parse_filename,
+                           errp);
     if (!bs) {
         goto done;
     }
@@ -3590,6 +3595,28 @@ done:
     return bs;
 }
 
+static BdrvChild *bdrv_open_child_common(const char *filename,
+                                         QDict *options, const char *bdref_key,
+                                         BlockDriverState *parent,
+                                         const BdrvChildClass *child_class,
+                                         BdrvChildRole child_role,
+                                         bool allow_none, bool parse_filename,
+                                         Error **errp)
+{
+    BlockDriverState *bs;
+
+    GLOBAL_STATE_CODE();
+
+    bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_class,
+                            child_role, allow_none, parse_filename, errp);
+    if (bs == NULL) {
+        return NULL;
+    }
+
+    return bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
+                             errp);
+}
+
 /*
  * Opens a disk image whose options are given as BlockdevRef in another block
  * device's options.
@@ -3611,18 +3638,9 @@ BdrvChild *bdrv_open_child(const char *filename,
                            BdrvChildRole child_role,
                            bool allow_none, Error **errp)
 {
-    BlockDriverState *bs;
-
-    GLOBAL_STATE_CODE();
-
-    bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_class,
-                            child_role, allow_none, errp);
-    if (bs == NULL) {
-        return NULL;
-    }
-
-    return bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
-                             errp);
+    return bdrv_open_child_common(filename, options, bdref_key, parent,
+                                  child_class, child_role, allow_none, false,
+                                  errp);
 }
 
 /*
@@ -3639,8 +3657,8 @@ int bdrv_open_file_child(const char *filename,
     role = parent->drv->is_filter ?
         (BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY) : BDRV_CHILD_IMAGE;
 
-    if (!bdrv_open_child(filename, options, bdref_key, parent,
-                         &child_of_bds, role, false, errp))
+    if (!bdrv_open_child_common(filename, options, bdref_key, parent,
+                                &child_of_bds, role, false, true, errp))
     {
         return -EINVAL;
     }
@@ -3685,7 +3703,8 @@ BlockDriverState *bdrv_open_blockdev_ref(BlockdevRef *ref, Error **errp)
 
     }
 
-    bs = bdrv_open_inherit(NULL, reference, qdict, 0, NULL, NULL, 0, errp);
+    bs = bdrv_open_inherit(NULL, reference, qdict, 0, NULL, NULL, 0, false,
+                           errp);
     obj = NULL;
     qobject_unref(obj);
     visit_free(v);
@@ -3775,7 +3794,7 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
                                            BlockDriverState *parent,
                                            const BdrvChildClass *child_class,
                                            BdrvChildRole child_role,
-                                           Error **errp)
+                                           bool parse_filename, Error **errp)
 {
     int ret;
     BlockBackend *file = NULL;
@@ -3819,9 +3838,11 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
     }
 
     /* json: syntax counts as explicit options, as if in the QDict */
-    parse_json_protocol(options, &filename, &local_err);
-    if (local_err) {
-        goto fail;
+    if (parse_filename) {
+        parse_json_protocol(options, &filename, &local_err);
+        if (local_err) {
+            goto fail;
+        }
     }
 
     bs->explicit_options = qdict_clone_shallow(options);
@@ -3846,7 +3867,8 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
                                      parent->open_flags, parent->options);
     }
 
-    ret = bdrv_fill_options(&options, filename, &flags, &local_err);
+    ret = bdrv_fill_options(&options, filename, &flags, parse_filename,
+                            &local_err);
     if (ret < 0) {
         goto fail;
     }
@@ -3915,7 +3937,7 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
 
         file_bs = bdrv_open_child_bs(filename, options, "file", bs,
                                      &child_of_bds, BDRV_CHILD_IMAGE,
-                                     true, &local_err);
+                                     true, true, &local_err);
         if (local_err) {
             goto fail;
         }
@@ -4062,7 +4084,7 @@ BlockDriverState *bdrv_open(const char *filename, const char *reference,
     GLOBAL_STATE_CODE();
 
     return bdrv_open_inherit(filename, reference, options, flags, NULL,
-                             NULL, 0, errp);
+                             NULL, 0, true, errp);
 }
 
 /* Return true if the NULL-terminated @list contains @str */