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Merge branch 'netlink-export-policy-on-validation-failures'

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Johannes Berg says:

====================
netlink: export policy on validation failures

Export the policy used for attribute validation when it fails,
so e.g. for an out-of-range attribute userspace immediately gets
the valid ranges back.

v2 incorporates the suggestion from Jakub to have a function to
estimate the size (netlink_policy_dump_attr_size_estimate()) and
check that it does the right thing on the *normal* policy dumps,
not (just) when calling it from the error scenario.

v3 only addresses a few minor style issues.

v4 fixes up a forgotten 'git add' ... sorry.

v5 is a resend, I messed up v4's cover letter subject (saying v3)
and apparently the second patch didn't go out at all.

Tested using nl80211/iw in a few scenarios, seems to work fine
and return the policy back, e.g.

kernel reports: integer out of range
policy: 04 00 0b 00 0c 00 04 00 01 00 00 00 00 00 00 00
        ^ padding
                    ^ minimum allowed value
policy: 04 00 0b 00 0c 00 05 00 ff ff ff ff 00 00 00 00
        ^ padding
                    ^ maximum allowed value
policy: 08 00 01 00 04 00 00 00
        ^ type 4 == U32

for an out-of-range case.
====================

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2020-10-09 20:22:49 -07:00
commit c77fb07fae
6 changed files with 162 additions and 56 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
include/linux/netlink.h
View File

@ -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); \
} 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); \
(extack)->policy = (pol); \
} \
} while (0)
#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)
{

4
include/net/netlink.h
View File

@ -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

2
include/uapi/linux/netlink.h
View File

@ -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

35
lib/nlattr.c
View File

@ -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;
}

5
net/netlink/af_netlink.c
View File

@ -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);

140
net/netlink/policy.c
View File

@ -196,49 +196,75 @@ bool netlink_policy_dump_loop(struct netlink_policy_dump_state *state)
return !netlink_policy_dump_finished(state);
}
/**
* netlink_policy_dump_write - write current policy dump attributes
* @skb: the message skb to write to
* @state: the policy dump state
*
* Returns: 0 on success, an error code otherwise
*/
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)
{
const struct nla_policy *pt;
struct nlattr *policy, *attr;
/* 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;
bool again;
struct nlattr *attr;
send_attribute:
again = false;
pt = &state->policies[state->policy_idx].policy[state->attr_idx];
policy = nla_nest_start(skb, state->policy_idx);
if (!policy)
return -ENOBUFS;
attr = nla_nest_start(skb, state->attr_idx);
attr = nla_nest_start(skb, nestattr);
if (!attr)
goto nla_put_failure;
return -ENOBUFS;
switch (pt->type) {
default:
case NLA_UNSPEC:
case NLA_REJECT:
/* skip - use NLA_MIN_LEN to advertise such */
nla_nest_cancel(skb, policy);
again = true;
goto next;
nla_nest_cancel(skb, attr);
return -ENODATA;
case NLA_NESTED:
type = NL_ATTR_TYPE_NESTED;
fallthrough;
case NLA_NESTED_ARRAY:
if (pt->type == NLA_NESTED_ARRAY)
type = NL_ATTR_TYPE_NESTED_ARRAY;
if (pt->nested_policy && pt->len &&
if (state && pt->nested_policy && pt->len &&
(nla_put_u32(skb, NL_POLICY_TYPE_ATTR_POLICY_IDX,
netlink_policy_dump_get_policy_idx(state,
pt->nested_policy,
@ -349,8 +375,66 @@ int netlink_policy_dump_write(struct sk_buff *skb,
if (nla_put_u32(skb, NL_POLICY_TYPE_ATTR_TYPE, type))
goto nla_put_failure;
/* finish and move state to next attribute */
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
* @state: the policy dump state
*
* Returns: 0 on success, an error code otherwise
*/
int netlink_policy_dump_write(struct sk_buff *skb,
struct netlink_policy_dump_state *state)
{
const struct nla_policy *pt;
struct nlattr *policy;
bool again;
int err;
send_attribute:
again = false;
pt = &state->policies[state->policy_idx].policy[state->attr_idx];
policy = nla_nest_start(skb, state->policy_idx);
if (!policy)
return -ENOBUFS;
err = __netlink_policy_dump_write_attr(state, skb, pt, state->attr_idx);
if (err == -ENODATA) {
nla_nest_cancel(skb, policy);
again = true;
goto next;
} else if (err) {
goto nla_put_failure;
}
/* finish and move state to next attribute */
nla_nest_end(skb, policy);
next: