Re: [PATCH v2 10/29] block/snapshot: Fix missing ERRP_GUARD() for error_prepend()

[Thomas Huth <thuth@redhat.com>]

On 11/03/2024 04.38, Zhao Liu wrote:
> From: Zhao Liu <zhao1.liu@intel.com>
> 
> 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/snapshot.c, there are 2 functions passing @errp to
> error_prepend() without ERRP_GUARD():
>   - bdrv_all_delete_snapshot()
>   - bdrv_all_goto_snapshot()
> 
> As the APIs exposed in include/block/snapshot.h, they could be called
> by other modules.
> 
> To avoid potential issues as [1] said, add missing ERRP_GUARD() at the
> beginning of these 2 functions.
> 
> [1]: Issue description in the commit message of commit ae7c80a7bd73
>       ("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>
> ---
>   block/snapshot.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/block/snapshot.c b/block/snapshot.c
> index 8694fc0a3eba..8242b4abac41 100644
> --- a/block/snapshot.c
> +++ b/block/snapshot.c
> @@ -566,6 +566,7 @@ int bdrv_all_delete_snapshot(const char *name,
>                                bool has_devices, strList *devices,
>                                Error **errp)
>   {
> +    ERRP_GUARD();
>       g_autoptr(GList) bdrvs = NULL;
>       GList *iterbdrvs;
>   
> @@ -605,6 +606,7 @@ int bdrv_all_goto_snapshot(const char *name,
>                              bool has_devices, strList *devices,
>                              Error **errp)
>   {
> +    ERRP_GUARD();
>       g_autoptr(GList) bdrvs = NULL;
>       GList *iterbdrvs;
>       int ret;

Reviewed-by: Thomas Huth <thuth@redhat.com>