Commit 1d99aa4e authored by Asbjørn Sloth Tønnesen's avatar Asbjørn Sloth Tønnesen Committed by Jakub Kicinski
Browse files

tools: ynl-gen: validate nested arrays 



In nested arrays don't require that the intermediate attribute
type should be a valid attribute type, it might just be zero
or an incrementing index, it is often not even used.

See include/net/netlink.h about NLA_NESTED_ARRAY:
> The difference to NLA_NESTED is the structure:
> NLA_NESTED has the nested attributes directly inside
> while an array has the nested attributes at another
> level down and the attribute types directly in the
> nesting don't matter.

Example based on include/uapi/linux/wireguard.h:
 > WGDEVICE_A_PEERS: NLA_NESTED
 >   0: NLA_NESTED
 >     WGPEER_A_PUBLIC_KEY: NLA_EXACT_LEN, len WG_KEY_LEN
 >     [..]
 >   0: NLA_NESTED
 >     ...
 >   ...

Previous the check required that the nested type was valid
in the parent attribute set, which in this case resolves to
WGDEVICE_A_UNSPEC, which is YNL_PT_REJECT, and it took the
early exit and returned YNL_PARSE_CB_ERROR.

This patch renames the old nl_attr_validate() to
__nl_attr_validate(), and creates a new inline function
nl_attr_validate() to mimic the old one.

The new __nl_attr_validate() takes the attribute type as an
argument, so we can use it to validate attributes of a
nested attribute, in the context of the parents attribute
type, which in the above case is generated as:
[WGDEVICE_A_PEERS] = {
  .name = "peers",
  .type = YNL_PT_NEST,
  .nest = &wireguard_wgpeer_nest,
},

__nl_attr_validate() only checks if the attribute length
is plausible for a given attribute type, so the .nest in
the above example is not used.

As the new inline function needs to be defined after
ynl_attr_type(), then the definitions are moved down,
so we avoid a forward declaration of ynl_attr_type().

Some other examples are NL80211_BAND_ATTR_FREQS (nest) and
NL80211_ATTR_SUPPORTED_COMMANDS (u32) both in nl80211-user.c
$ make -C tools/net/ynl/generated nl80211-user.c

Signed-off-by: default avatarAsbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: default avatarJakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20250915144301.725949-7-ast@fiberby.net


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 099902fc

tools/net/ynl/lib/ynl-priv.h

+9 −1
Original line number Diff line number Diff line
@@ -106,7 +106,6 @@ ynl_gemsg_start_req(struct ynl_sock *ys, __u32 id, __u8 cmd, __u8 version); 
struct nlmsghdr *

ynl_gemsg_start_dump(struct ynl_sock *ys, __u32 id, __u8 cmd, __u8 version);



int ynl_attr_validate(struct ynl_parse_arg *yarg, const struct nlattr *attr);

int ynl_submsg_failed(struct ynl_parse_arg *yarg, const char *field_name,

		      const char *sel_name);
@@ -467,4 +466,13 @@ ynl_attr_put_sint(struct nlmsghdr *nlh, __u16 type, __s64 data) 
	else

		ynl_attr_put_s64(nlh, type, data);

}



int __ynl_attr_validate(struct ynl_parse_arg *yarg, const struct nlattr *attr,

			unsigned int type);



static inline int ynl_attr_validate(struct ynl_parse_arg *yarg,

				    const struct nlattr *attr)

{

	return __ynl_attr_validate(yarg, attr, ynl_attr_type(attr));

}

#endif

tools/net/ynl/lib/ynl.c

+3 −3
Original line number Diff line number Diff line
@@ -360,15 +360,15 @@ static int ynl_cb_done(const struct nlmsghdr *nlh, struct ynl_parse_arg *yarg) 


/* Attribute validation */



int ynl_attr_validate(struct ynl_parse_arg *yarg, const struct nlattr *attr)

int __ynl_attr_validate(struct ynl_parse_arg *yarg, const struct nlattr *attr,

			unsigned int type)

{

	const struct ynl_policy_attr *policy;

	unsigned int type, len;

	unsigned char *data;

	unsigned int len;



	data = ynl_attr_data(attr);

	len = ynl_attr_data_len(attr);

	type = ynl_attr_type(attr);

	if (type > yarg->rsp_policy->max_attr) {

		yerr(yarg->ys, YNL_ERROR_INTERNAL,

		     "Internal error, validating unknown attribute");

tools/net/ynl/pyynl/ynl_gen_c.py

+1 −1
Original line number Diff line number Diff line
@@ -830,7 +830,7 @@ class TypeArrayNest(Type): 
        local_vars = ['const struct nlattr *attr2;']

        get_lines = [f'attr_{self.c_name} = attr;',

                     'ynl_attr_for_each_nested(attr2, attr) {',

                     '\tif (ynl_attr_validate(yarg, attr2))',

                     '\tif (__ynl_attr_validate(yarg, attr2, type))',

                     '\t\treturn YNL_PARSE_CB_ERROR;',

                     f'\tn_{self.c_name}++;',

                     '}']