Re: [Qemu-devel] [PATCH v5 23/28] qapi: More rigorous checking for type safety bypass

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> Now that we have a way to validate every type, we can also be
> stricter about enforcing that callers that want to bypass
> type safety in generated code.  Prior to this patch, it didn't
> matter what value was associated with the key 'gen', but it
> looked odd that 'gen':'yes' could result in bypassing the
> generated code.  These changes also enforce the changes made
> earlier in the series for documentation and consolidation of
> using '**' as the wildcard type, as well as 'gen':false as the
> canonical spelling for requesting type bypass.
>
> Signed-off-by: Eric Blake <address@hidden>
> ---
>  scripts/qapi.py                            | 23 ++++++++++++++++++-----
>  tests/qapi-schema/type-bypass-bad-gen.err  |  1 +
>  tests/qapi-schema/type-bypass-bad-gen.exit |  2 +-
>  tests/qapi-schema/type-bypass-bad-gen.json |  2 +-
>  tests/qapi-schema/type-bypass-bad-gen.out  |  3 ---
>  tests/qapi-schema/type-bypass-no-gen.err   |  1 +
>  tests/qapi-schema/type-bypass-no-gen.exit  |  2 +-
>  tests/qapi-schema/type-bypass-no-gen.json  |  2 +-
>  tests/qapi-schema/type-bypass-no-gen.out   |  3 ---
>  9 files changed, 24 insertions(+), 15 deletions(-)
>
> diff --git a/scripts/qapi.py b/scripts/qapi.py
> index 9421431..800e8e4 100644
> --- a/scripts/qapi.py
> +++ b/scripts/qapi.py
> @@ -321,13 +321,14 @@ def check_name(expr_info, source, name, allow_optional 
> = False):
>                              "%s uses invalid name '%s'" % (source, name))
>
>  def check_type(expr_info, source, data, allow_array = False,
> -               allowed_metas = [], allow_dict = True, allow_optional = 
> False):
> +               allowed_metas = [], allow_dict = True, allow_optional = False,
> +               allow_star = False):
>      global all_names
>
>      if data is None:
>          return
>
> -    if data == '**':
> +    if allow_star and data == '**':
>          return
>
>      # Check if array type for data is okay

Aha!  Takes us back to my question on PATCH 21.

State so far: check_name() accepts '**', but some of its callers reject
it.  Whether it's rejected everywhere we don't want it isn't obvious,
even if we add rejects that are currently missing.

Perhaps we should try to do this the other way round: require extra code
in places where we want to accept it.

I can accept this as is, because it's an improvement, and we can plug
remaining holes on top.

> @@ -343,6 +344,10 @@ def check_type(expr_info, source, data, allow_array = 
> False,
>
>      # Check if type name for data is okay
>      if isinstance(data, str):
> +        if data == '**':
> +            raise QAPIExprError(expr_info,
> +                                "%s uses '**' but did not request 
> 'gen':false"
> +                                % source)
>          if not data in all_names:
>              raise QAPIExprError(expr_info,
>                                  "%s uses unknown type '%s'"
> @@ -367,19 +372,23 @@ def check_type(expr_info, source, data, allow_array = 
> False,
>                     allow_array=True,
>                     allowed_metas=['built-in', 'union', 'alternate', 'struct',
>                                    'enum'],
> -                   allow_dict=True, allow_optional=True)
> +                   allow_dict=True, allow_optional=True, 
> allow_star=allow_star)
>
>  def check_command(expr, expr_info):
>      name = expr['command']
> +    allow_star = expr.has_key('gen')
> +
>      check_type(expr_info, "'data' for command '%s'" % name,
>                 expr.get('data'),
> -               allowed_metas=['union', 'struct'], allow_optional=True)
> +               allowed_metas=['union', 'struct'], allow_optional=True,
> +               allow_star=allow_star)
>      returns_meta = ['union', 'struct']
>      if name in returns_whitelist:
>          returns_meta += ['built-in', 'alternate', 'enum']
>      check_type(expr_info, "'returns' for command '%s'" % name,
>                 expr.get('returns'), allow_array=True,
> -               allowed_metas=returns_meta, allow_optional=True)
> +               allowed_metas=returns_meta, allow_optional=True,
> +               allow_star=allow_star)
>
>  def check_event(expr, expr_info):
>      global events
> @@ -574,6 +583,10 @@ def check_keys(expr_elem, meta, required, optional=[]):
>              raise QAPIExprError(info,
>                                  "%s '%s' has unknown key '%s'"
>                                  % (meta, name, key))
> +        if (key == 'gen' or key == 'success-response') and value != False:
> +            raise QAPIExprError(info,
> +                                "'%s' of %s '%s' should only use false value"
> +                                % (key, meta, name))
>      for key in required:
>          if not expr.has_key(key):
>              raise QAPIExprError(info,
> diff --git a/tests/qapi-schema/type-bypass-bad-gen.err 
> b/tests/qapi-schema/type-bypass-bad-gen.err
> index e69de29..a83c3c6 100644
> --- a/tests/qapi-schema/type-bypass-bad-gen.err
> +++ b/tests/qapi-schema/type-bypass-bad-gen.err
> @@ -0,0 +1 @@
> +tests/qapi-schema/type-bypass-bad-gen.json:2: 'gen' of command 'foo' should 
> only use false value
> diff --git a/tests/qapi-schema/type-bypass-bad-gen.exit 
> b/tests/qapi-schema/type-bypass-bad-gen.exit
> index 573541a..d00491f 100644
> --- a/tests/qapi-schema/type-bypass-bad-gen.exit
> +++ b/tests/qapi-schema/type-bypass-bad-gen.exit
> @@ -1 +1 @@
> -0
> +1
> diff --git a/tests/qapi-schema/type-bypass-bad-gen.json 
> b/tests/qapi-schema/type-bypass-bad-gen.json
> index bb70bee..e8dec34 100644
> --- a/tests/qapi-schema/type-bypass-bad-gen.json
> +++ b/tests/qapi-schema/type-bypass-bad-gen.json
> @@ -1,2 +1,2 @@
> -# FIXME: 'gen' should only appear with value false
> +# 'gen' should only appear with value false
>  { 'command': 'foo', 'gen': 'whatever' }
> diff --git a/tests/qapi-schema/type-bypass-bad-gen.out 
> b/tests/qapi-schema/type-bypass-bad-gen.out
> index e678f2c..e69de29 100644
> --- a/tests/qapi-schema/type-bypass-bad-gen.out
> +++ b/tests/qapi-schema/type-bypass-bad-gen.out
> @@ -1,3 +0,0 @@
> -[OrderedDict([('command', 'foo'), ('gen', 'whatever')])]
> -[]
> -[]
> diff --git a/tests/qapi-schema/type-bypass-no-gen.err 
> b/tests/qapi-schema/type-bypass-no-gen.err
> index e69de29..20cef0a 100644
> --- a/tests/qapi-schema/type-bypass-no-gen.err
> +++ b/tests/qapi-schema/type-bypass-no-gen.err
> @@ -0,0 +1 @@
> +tests/qapi-schema/type-bypass-no-gen.json:2: Member 'arg' of 'data' for 
> command 'unsafe' uses '**' but did not request 'gen':false
> diff --git a/tests/qapi-schema/type-bypass-no-gen.exit 
> b/tests/qapi-schema/type-bypass-no-gen.exit
> index 573541a..d00491f 100644
> --- a/tests/qapi-schema/type-bypass-no-gen.exit
> +++ b/tests/qapi-schema/type-bypass-no-gen.exit
> @@ -1 +1 @@
> -0
> +1
> diff --git a/tests/qapi-schema/type-bypass-no-gen.json 
> b/tests/qapi-schema/type-bypass-no-gen.json
> index af87c19..49b5742 100644
> --- a/tests/qapi-schema/type-bypass-no-gen.json
> +++ b/tests/qapi-schema/type-bypass-no-gen.json
> @@ -1,2 +1,2 @@
> -# FIXME: type bypass should only work with 'gen':false
> +# type bypass only works with 'gen':'no'

'gen': false

>  { 'command': 'unsafe', 'data': { 'arg': '**' }, 'returns': '**' }
> diff --git a/tests/qapi-schema/type-bypass-no-gen.out 
> b/tests/qapi-schema/type-bypass-no-gen.out
> index 8b2a9ac..e69de29 100644
> --- a/tests/qapi-schema/type-bypass-no-gen.out
> +++ b/tests/qapi-schema/type-bypass-no-gen.out
> @@ -1,3 +0,0 @@
> -[OrderedDict([('command', 'unsafe'), ('data', OrderedDict([('arg', '**')])), 
> ('returns', '**')])]
> -[]
> -[]

With the trivial fix in type-bypass-no-gen.json:

Reviewed-by: Markus Armbruster <address@hidden>