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block: Fix missing ERRP_GUARD() for error_prepend()

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As the comment in qapi/error, passing @errp to error_prepend() requires
ERRP_GUARD():

* = Why, when and how to use ERRP_GUARD() =
*
* Without ERRP_GUARD(), use of the @errp parameter is restricted:
...
* - It should not be passed to error_prepend(), error_vprepend() or
*   error_append_hint(), because that doesn't work with &error_fatal.
* ERRP_GUARD() lifts these restrictions.
*
* To use ERRP_GUARD(), add it right at the beginning of the function.
* @errp can then be used without worrying about the argument being
* NULL or &error_fatal.

ERRP_GUARD() could avoid the case when @errp is &error_fatal, the user
can't see this additional information, because exit() happens in
error_setg earlier than information is added [1].

In block.c, there are 4 functions passing @errp to error_prepend()
without ERRP_GUARD():
 - bdrv_co_create_opts_simple()
 - parse_json_filename()
 - bdrv_open_backing_file()
 - bdrv_append_temp_snapshot()

bdrv_co_create_opts_simple(), is an implementation of
BlockDriver.bdrv_co_create_opts(). There are too many possible callers
to check the impact of this defect; it may or may not be harmless. Thus
it is necessary to protect @errp with ERRP_GUARD().

Though the @errp parameters passed to parse_json_filename(),
bdrv_open_backing_file() and bdrv_append_temp_snapshot() points to their
callers' local_err, to follow the requirement of @errp, also add missing
ERRP_GUARD() at their beginning.

[1]: Issue description in the commit message of commit ae7c80a7bd
     ("error: New macro ERRP_GUARD()").

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Hanna Reitz <hreitz@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-ID: <20240311033822.3142585-4-zhao1.liu@linux.intel.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
This commit is contained in:
Zhao Liu 2024-03-11 11:37:56 +08:00 committed by Thomas Huth
parent c1cccad865
commit 7b22e05582
1 changed files with 4 additions and 0 deletions
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4
block.c
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@ -633,6 +633,7 @@ int coroutine_fn bdrv_co_create_opts_simple(BlockDriver *drv,
QemuOpts *opts,
Error **errp)
{
ERRP_GUARD();
BlockBackend *blk;
QDict *options;
int64_t size = 0;
@ -1998,6 +1999,7 @@ fail_opts:
static QDict *parse_json_filename(const char *filename, Error **errp)
{
ERRP_GUARD();
QObject *options_obj;
QDict *options;
int ret;
@ -3585,6 +3587,7 @@ int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
const char *bdref_key, Error **errp)
{
ERRP_GUARD();
char *backing_filename = NULL;
char *bdref_key_dot;
const char *reference = NULL;
@ -3851,6 +3854,7 @@ static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs,
QDict *snapshot_options,
Error **errp)
{
ERRP_GUARD();
g_autofree char *tmp_filename = NULL;
int64_t total_size;
QemuOpts *opts = NULL;