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netlink: Add strict version of nlmsg_parse and nla_parse 

nla_parse is currently lenient on message parsing, allowing type to be 0
or greater than max expected and only logging a message

    "netlink: %d bytes leftover after parsing attributes in process `%s'."

if the netlink message has unknown data at the end after parsing. What this
could mean is that the header at the front of the attributes is actually
wrong and the parsing is shifted from what is expected.

Add a new strict version that actually fails with EINVAL if there are any
bytes remaining after the parsing loop completes, if the atttrbitue type
is 0 or greater than max expected.

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Ahern 2018-10-07 20:16:25 -07:00 committed by David S. Miller
parent dac9c9790e
commit a5f6cba291
2 changed files with 54 additions and 13 deletions
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17
include/net/netlink.h
View File

@ -373,6 +373,9 @@ int nla_validate(const struct nlattr *head, int len, int maxtype,
int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head, int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
int len, const struct nla_policy *policy, int len, const struct nla_policy *policy,
struct netlink_ext_ack *extack); struct netlink_ext_ack *extack);
int nla_parse_strict(struct nlattr **tb, int maxtype, const struct nlattr *head,
int len, const struct nla_policy *policy,
struct netlink_ext_ack *extack);
int nla_policy_len(const struct nla_policy *, int); int nla_policy_len(const struct nla_policy *, int);
struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype); struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype);
size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize); size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize);
@ -525,6 +528,20 @@ static inline int nlmsg_parse(const struct nlmsghdr *nlh, int hdrlen,
nlmsg_attrlen(nlh, hdrlen), policy, extack); nlmsg_attrlen(nlh, hdrlen), policy, extack);
} }
static inline int nlmsg_parse_strict(const struct nlmsghdr *nlh, int hdrlen,
struct nlattr *tb[], int maxtype,
const struct nla_policy *policy,
struct netlink_ext_ack *extack)
{
if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen)) {
NL_SET_ERR_MSG(extack, "Invalid header length");
return -EINVAL;
}
return nla_parse_strict(tb, maxtype, nlmsg_attrdata(nlh, hdrlen),
nlmsg_attrlen(nlh, hdrlen), policy, extack);
}
/** /**
* nlmsg_find_attr - find a specific attribute in a netlink message * nlmsg_find_attr - find a specific attribute in a netlink message
* @nlh: netlink message header * @nlh: netlink message header

50
lib/nlattr.c
View File

@ -391,9 +391,10 @@ EXPORT_SYMBOL(nla_policy_len);
* *
* Returns 0 on success or a negative error code. * Returns 0 on success or a negative error code.
*/ */
int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head, static int __nla_parse(struct nlattr **tb, int maxtype,
int len, const struct nla_policy *policy, const struct nlattr *head, int len,
struct netlink_ext_ack *extack) bool strict, const struct nla_policy *policy,
struct netlink_ext_ack *extack)
{ {
const struct nlattr *nla; const struct nlattr *nla;
int rem; int rem;
@ -403,27 +404,50 @@ int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
nla_for_each_attr(nla, head, len, rem) { nla_for_each_attr(nla, head, len, rem) {
u16 type = nla_type(nla); u16 type = nla_type(nla);
if (type > 0 && type <= maxtype) { if (type == 0 || type > maxtype) {
if (policy) { if (strict) {
int err = validate_nla(nla, maxtype, policy, NL_SET_ERR_MSG(extack, "Unknown attribute type");
extack); return -EINVAL;
if (err < 0)
return err;
} }
continue;
tb[type] = (struct nlattr *)nla;
} }
if (policy) {
int err = validate_nla(nla, maxtype, policy, extack);
if (err < 0)
return err;
}
tb[type] = (struct nlattr *)nla;
} }
if (unlikely(rem > 0)) if (unlikely(rem > 0)) {
pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n", pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
rem, current->comm); rem, current->comm);
NL_SET_ERR_MSG(extack, "bytes leftover after parsing attributes");
if (strict)
return -EINVAL;
}
return 0; return 0;
} }
int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
int len, const struct nla_policy *policy,
struct netlink_ext_ack *extack)
{
return __nla_parse(tb, maxtype, head, len, false, policy, extack);
}
EXPORT_SYMBOL(nla_parse); EXPORT_SYMBOL(nla_parse);
int nla_parse_strict(struct nlattr **tb, int maxtype, const struct nlattr *head,
int len, const struct nla_policy *policy,
struct netlink_ext_ack *extack)
{
return __nla_parse(tb, maxtype, head, len, true, policy, extack);
}
EXPORT_SYMBOL(nla_parse_strict);
/** /**
* nla_find - Find a specific attribute in a stream of attributes * nla_find - Find a specific attribute in a stream of attributes
* @head: head of attribute stream * @head: head of attribute stream