From 44f3625bc61653ea3bde9960298faf2f5518fda5 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Thu, 8 Oct 2020 12:45:17 +0200 Subject: netlink: export policy in extended ACK Add a new attribute NLMSGERR_ATTR_POLICY to the extended ACK to advertise the policy, e.g. if an attribute was out of range, you'll know the range that's permissible. Add new NL_SET_ERR_MSG_ATTR_POL() and NL_SET_ERR_MSG_ATTR_POL() macros to set this, since realistically it's only useful to do this when the bad attribute (offset) is also returned. Use it in lib/nlattr.c which practically does all the policy validation. v2: - add and use netlink_policy_dump_attr_size_estimate() v3: - remove redundant break v4: - really remove redundant break ... sorry Reviewed-by: Jakub Kicinski Signed-off-by: Johannes Berg Signed-off-by: Jakub Kicinski --- include/linux/netlink.h | 30 ++++++++++++++-------- include/net/netlink.h | 4 +++ include/uapi/linux/netlink.h | 2 ++ lib/nlattr.c | 35 +++++++++++++------------ net/netlink/af_netlink.c | 5 ++++ net/netlink/policy.c | 61 ++++++++++++++++++++++++++++++++++++++++++++ 6 files changed, 110 insertions(+), 27 deletions(-) diff --git a/include/linux/netlink.h b/include/linux/netlink.h index e3e49f0e5c13..666cd0390699 100644 --- a/include/linux/netlink.h +++ b/include/linux/netlink.h @@ -68,12 +68,14 @@ netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg) * @_msg: message string to report - don't access directly, use * %NL_SET_ERR_MSG * @bad_attr: attribute with error + * @policy: policy for a bad attribute * @cookie: cookie data to return to userspace (for success) * @cookie_len: actual cookie data length */ struct netlink_ext_ack { const char *_msg; const struct nlattr *bad_attr; + const struct nla_policy *policy; u8 cookie[NETLINK_MAX_COOKIE_LEN]; u8 cookie_len; }; @@ -95,21 +97,29 @@ struct netlink_ext_ack { #define NL_SET_ERR_MSG_MOD(extack, msg) \ NL_SET_ERR_MSG((extack), KBUILD_MODNAME ": " msg) -#define NL_SET_BAD_ATTR(extack, attr) do { \ - if ((extack)) \ +#define NL_SET_BAD_ATTR_POLICY(extack, attr, pol) do { \ + if ((extack)) { \ (extack)->bad_attr = (attr); \ + (extack)->policy = (pol); \ + } \ } while (0) -#define NL_SET_ERR_MSG_ATTR(extack, attr, msg) do { \ - static const char __msg[] = msg; \ - struct netlink_ext_ack *__extack = (extack); \ - \ - if (__extack) { \ - __extack->_msg = __msg; \ - __extack->bad_attr = (attr); \ - } \ +#define NL_SET_BAD_ATTR(extack, attr) NL_SET_BAD_ATTR_POLICY(extack, attr, NULL) + +#define NL_SET_ERR_MSG_ATTR_POL(extack, attr, pol, msg) do { \ + static const char __msg[] = msg; \ + struct netlink_ext_ack *__extack = (extack); \ + \ + if (__extack) { \ + __extack->_msg = __msg; \ + __extack->bad_attr = (attr); \ + __extack->policy = (pol); \ + } \ } while (0) +#define NL_SET_ERR_MSG_ATTR(extack, attr, msg) \ + NL_SET_ERR_MSG_ATTR_POL(extack, attr, NULL, msg) + static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack, u64 cookie) { diff --git a/include/net/netlink.h b/include/net/netlink.h index 2b9e41075f19..7356f41d23ba 100644 --- a/include/net/netlink.h +++ b/include/net/netlink.h @@ -1957,6 +1957,10 @@ int netlink_policy_dump_get_policy_idx(struct netlink_policy_dump_state *state, bool netlink_policy_dump_loop(struct netlink_policy_dump_state *state); int netlink_policy_dump_write(struct sk_buff *skb, struct netlink_policy_dump_state *state); +int netlink_policy_dump_attr_size_estimate(const struct nla_policy *pt); +int netlink_policy_dump_write_attr(struct sk_buff *skb, + const struct nla_policy *pt, + int nestattr); void netlink_policy_dump_free(struct netlink_policy_dump_state *state); #endif diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h index d02e472ba54c..c3816ff7bfc3 100644 --- a/include/uapi/linux/netlink.h +++ b/include/uapi/linux/netlink.h @@ -129,6 +129,7 @@ struct nlmsgerr { * @NLMSGERR_ATTR_COOKIE: arbitrary subsystem specific cookie to * be used - in the success case - to identify a created * object or operation or similar (binary) + * @NLMSGERR_ATTR_POLICY: policy for a rejected attribute * @__NLMSGERR_ATTR_MAX: number of attributes * @NLMSGERR_ATTR_MAX: highest attribute number */ @@ -137,6 +138,7 @@ enum nlmsgerr_attrs { NLMSGERR_ATTR_MSG, NLMSGERR_ATTR_OFFS, NLMSGERR_ATTR_COOKIE, + NLMSGERR_ATTR_POLICY, __NLMSGERR_ATTR_MAX, NLMSGERR_ATTR_MAX = __NLMSGERR_ATTR_MAX - 1 diff --git a/lib/nlattr.c b/lib/nlattr.c index 9c99f5daa4d2..74019c8ebf6b 100644 --- a/lib/nlattr.c +++ b/lib/nlattr.c @@ -96,8 +96,8 @@ static int nla_validate_array(const struct nlattr *head, int len, int maxtype, continue; if (nla_len(entry) < NLA_HDRLEN) { - NL_SET_ERR_MSG_ATTR(extack, entry, - "Array element too short"); + NL_SET_ERR_MSG_ATTR_POL(extack, entry, policy, + "Array element too short"); return -ERANGE; } @@ -195,8 +195,8 @@ static int nla_validate_range_unsigned(const struct nla_policy *pt, pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n", current->comm, pt->type); if (validate & NL_VALIDATE_STRICT_ATTRS) { - NL_SET_ERR_MSG_ATTR(extack, nla, - "invalid attribute length"); + NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt, + "invalid attribute length"); return -EINVAL; } @@ -208,11 +208,11 @@ static int nla_validate_range_unsigned(const struct nla_policy *pt, bool binary = pt->type == NLA_BINARY; if (binary) - NL_SET_ERR_MSG_ATTR(extack, nla, - "binary attribute size out of range"); + NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt, + "binary attribute size out of range"); else - NL_SET_ERR_MSG_ATTR(extack, nla, - "integer out of range"); + NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt, + "integer out of range"); return -ERANGE; } @@ -291,8 +291,8 @@ static int nla_validate_int_range_signed(const struct nla_policy *pt, nla_get_range_signed(pt, &range); if (value < range.min || value > range.max) { - NL_SET_ERR_MSG_ATTR(extack, nla, - "integer out of range"); + NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt, + "integer out of range"); return -ERANGE; } @@ -377,8 +377,8 @@ static int validate_nla(const struct nlattr *nla, int maxtype, pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n", current->comm, type); if (validate & NL_VALIDATE_STRICT_ATTRS) { - NL_SET_ERR_MSG_ATTR(extack, nla, - "invalid attribute length"); + NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt, + "invalid attribute length"); return -EINVAL; } } @@ -386,14 +386,14 @@ static int validate_nla(const struct nlattr *nla, int maxtype, if (validate & NL_VALIDATE_NESTED) { if ((pt->type == NLA_NESTED || pt->type == NLA_NESTED_ARRAY) && !(nla->nla_type & NLA_F_NESTED)) { - NL_SET_ERR_MSG_ATTR(extack, nla, - "NLA_F_NESTED is missing"); + NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt, + "NLA_F_NESTED is missing"); return -EINVAL; } if (pt->type != NLA_NESTED && pt->type != NLA_NESTED_ARRAY && pt->type != NLA_UNSPEC && (nla->nla_type & NLA_F_NESTED)) { - NL_SET_ERR_MSG_ATTR(extack, nla, - "NLA_F_NESTED not expected"); + NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt, + "NLA_F_NESTED not expected"); return -EINVAL; } } @@ -550,7 +550,8 @@ static int validate_nla(const struct nlattr *nla, int maxtype, return 0; out_err: - NL_SET_ERR_MSG_ATTR(extack, nla, "Attribute failed policy validation"); + NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt, + "Attribute failed policy validation"); return err; } diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index df675a8e1918..daca50d6bb12 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2420,6 +2420,8 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err, tlvlen += nla_total_size(sizeof(u32)); if (nlk_has_extack && extack && extack->cookie_len) tlvlen += nla_total_size(extack->cookie_len); + if (err && nlk_has_extack && extack && extack->policy) + tlvlen += netlink_policy_dump_attr_size_estimate(extack->policy); if (tlvlen) flags |= NLM_F_ACK_TLVS; @@ -2452,6 +2454,9 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err, if (extack->cookie_len) WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE, extack->cookie_len, extack->cookie)); + if (extack->policy) + netlink_policy_dump_write_attr(skb, extack->policy, + NLMSGERR_ATTR_POLICY); } nlmsg_end(skb, rep); diff --git a/net/netlink/policy.c b/net/netlink/policy.c index 4383436759e2..8d7c900e27f4 100644 --- a/net/netlink/policy.c +++ b/net/netlink/policy.c @@ -196,12 +196,54 @@ bool netlink_policy_dump_loop(struct netlink_policy_dump_state *state) return !netlink_policy_dump_finished(state); } +int netlink_policy_dump_attr_size_estimate(const struct nla_policy *pt) +{ + /* nested + type */ + int common = 2 * nla_attr_size(sizeof(u32)); + + switch (pt->type) { + case NLA_UNSPEC: + case NLA_REJECT: + /* these actually don't need any space */ + return 0; + case NLA_NESTED: + case NLA_NESTED_ARRAY: + /* common, policy idx, policy maxattr */ + return common + 2 * nla_attr_size(sizeof(u32)); + case NLA_U8: + case NLA_U16: + case NLA_U32: + case NLA_U64: + case NLA_MSECS: + case NLA_S8: + case NLA_S16: + case NLA_S32: + case NLA_S64: + /* maximum is common, u64 min/max with padding */ + return common + + 2 * (nla_attr_size(0) + nla_attr_size(sizeof(u64))); + case NLA_BITFIELD32: + return common + nla_attr_size(sizeof(u32)); + case NLA_STRING: + case NLA_NUL_STRING: + case NLA_BINARY: + /* maximum is common, u32 min-length/max-length */ + return common + 2 * nla_attr_size(sizeof(u32)); + case NLA_FLAG: + return common; + } + + /* this should then cause a warning later */ + return 0; +} + static int __netlink_policy_dump_write_attr(struct netlink_policy_dump_state *state, struct sk_buff *skb, const struct nla_policy *pt, int nestattr) { + int estimate = netlink_policy_dump_attr_size_estimate(pt); enum netlink_attribute_type type; struct nlattr *attr; @@ -334,12 +376,31 @@ __netlink_policy_dump_write_attr(struct netlink_policy_dump_state *state, goto nla_put_failure; nla_nest_end(skb, attr); + WARN_ON(attr->nla_len > estimate); + return 0; nla_put_failure: nla_nest_cancel(skb, attr); return -ENOBUFS; } +/** + * netlink_policy_dump_write_attr - write a given attribute policy + * @skb: the message skb to write to + * @pt: the attribute's policy + * @nestattr: the nested attribute ID to use + * + * Returns: 0 on success, an error code otherwise; -%ENODATA is + * special, indicating that there's no policy data and + * the attribute is generally rejected. + */ +int netlink_policy_dump_write_attr(struct sk_buff *skb, + const struct nla_policy *pt, + int nestattr) +{ + return __netlink_policy_dump_write_attr(NULL, skb, pt, nestattr); +} + /** * netlink_policy_dump_write - write current policy dump attributes * @skb: the message skb to write to -- cgit v1.2.3