From 53153ebcf066e962cd73d7fcfeca53039be2a945 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 25 Apr 2024 14:56:02 +0200 Subject: [PATCH 4/4] block: Parse filenames only when explicitly requested RH-Author: Hana Czenczek RH-MergeRequest: 1: CVE 2024-4467 (PRDSC) RH-Jira: RHEL-46239 RH-CVE: CVE-2024-4467 RH-Acked-by: Kevin Wolf RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Eric Blake RH-Commit: [4/4] f44c2941d4419e60f16dea3e9adca164e75aa78d 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. Signed-off-by: Kevin Wolf Reviewed-by: Eric Blake Reviewed-by: Stefan Hajnoczi Reviewed-by: Hanna Czenczek Upstream: N/A, embargoed Signed-off-by: Hanna Czenczek --- block.c | 90 ++++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 57 insertions(+), 33 deletions(-) diff --git a/block.c b/block.c index 468cf5e67d..50bdd197b7 100644 --- a/block.c +++ b/block.c @@ -86,6 +86,7 @@ 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, @@ -2058,7 +2059,8 @@ 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; @@ -2100,7 +2102,7 @@ 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"); @@ -3663,7 +3665,8 @@ 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: "); @@ -3697,7 +3700,8 @@ 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; @@ -3728,7 +3732,8 @@ 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; } @@ -3738,6 +3743,33 @@ 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; + BdrvChild *child; + + 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; + } + + bdrv_graph_wrlock(); + child = bdrv_attach_child(parent, bs, bdref_key, child_class, child_role, + errp); + bdrv_graph_wrunlock(); + + return child; +} + /* * Opens a disk image whose options are given as BlockdevRef in another block * device's options. @@ -3761,27 +3793,15 @@ BdrvChild *bdrv_open_child(const char *filename, BdrvChildRole child_role, bool allow_none, Error **errp) { - BlockDriverState *bs; - BdrvChild *child; - - 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; - } - - bdrv_graph_wrlock(); - child = bdrv_attach_child(parent, bs, bdref_key, child_class, child_role, - errp); - bdrv_graph_wrunlock(); - - return child; + return bdrv_open_child_common(filename, options, bdref_key, parent, + child_class, child_role, allow_none, false, + errp); } /* - * Wrapper on bdrv_open_child() for most popular case: open primary child of bs. + * This does mostly the same as bdrv_open_child(), but for opening the primary + * child of a node. A notable difference from bdrv_open_child() is that it + * enables filename parsing for protocol names (including json:). * * @parent can move to a different AioContext in this function. */ @@ -3796,8 +3816,8 @@ 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; } @@ -3842,7 +3862,8 @@ 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); @@ -3932,7 +3953,7 @@ static BlockDriverState * no_coroutine_fn bdrv_open_inherit(const char *filename, const char *reference, QDict *options, int flags, BlockDriverState *parent, const BdrvChildClass *child_class, BdrvChildRole child_role, - Error **errp) + bool parse_filename, Error **errp) { int ret; BlockBackend *file = NULL; @@ -3980,9 +4001,11 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options, } /* 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); @@ -4007,7 +4030,8 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options, 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; } @@ -4076,7 +4100,7 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options, 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; } @@ -4225,7 +4249,7 @@ 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 */ -- 2.39.3