[NETLINK]: Improve string attribute validation
Introduces a new attribute type NLA_NUL_STRING to support NUL
terminated strings. Attributes of this kind require to carry
a terminating NUL within the maximum specified in the policy.
The `old' NLA_STRING which is not required to be NUL terminated
is extended to provide means to specify a maximum length of the
string.
Aims at easing the pain with using nla_strlcpy() on temporary
buffers.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/netlink.h b/include/net/netlink.h
index bcb27e3..11dc2e7 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -167,6 +167,7 @@
NLA_FLAG,
NLA_MSECS,
NLA_NESTED,
+ NLA_NUL_STRING,
__NLA_TYPE_MAX,
};
@@ -175,21 +176,27 @@
/**
* struct nla_policy - attribute validation policy
* @type: Type of attribute or NLA_UNSPEC
- * @minlen: Minimal length of payload required to be available
+ * @len: Type specific length of payload
*
* Policies are defined as arrays of this struct, the array must be
* accessible by attribute type up to the highest identifier to be expected.
*
+ * Meaning of `len' field:
+ * NLA_STRING Maximum length of string
+ * NLA_NUL_STRING Maximum length of string (excluding NUL)
+ * NLA_FLAG Unused
+ * All other Exact length of attribute payload
+ *
* Example:
* static struct nla_policy my_policy[ATTR_MAX+1] __read_mostly = {
* [ATTR_FOO] = { .type = NLA_U16 },
- * [ATTR_BAR] = { .type = NLA_STRING },
- * [ATTR_BAZ] = { .minlen = sizeof(struct mystruct) },
+ * [ATTR_BAR] = { .type = NLA_STRING, len = BARSIZ },
+ * [ATTR_BAZ] = { .len = sizeof(struct mystruct) },
* };
*/
struct nla_policy {
u16 type;
- u16 minlen;
+ u16 len;
};
/**
diff --git a/net/netlink/attr.c b/net/netlink/attr.c
index 136e529..0041395 100644
--- a/net/netlink/attr.c
+++ b/net/netlink/attr.c
@@ -20,7 +20,6 @@
[NLA_U16] = sizeof(u16),
[NLA_U32] = sizeof(u32),
[NLA_U64] = sizeof(u64),
- [NLA_STRING] = 1,
[NLA_NESTED] = NLA_HDRLEN,
};
@@ -28,7 +27,7 @@
struct nla_policy *policy)
{
struct nla_policy *pt;
- int minlen = 0;
+ int minlen = 0, attrlen = nla_len(nla);
if (nla->nla_type <= 0 || nla->nla_type > maxtype)
return 0;
@@ -37,16 +36,46 @@
BUG_ON(pt->type > NLA_TYPE_MAX);
- if (pt->minlen)
- minlen = pt->minlen;
- else if (pt->type != NLA_UNSPEC)
- minlen = nla_attr_minlen[pt->type];
+ switch (pt->type) {
+ case NLA_FLAG:
+ if (attrlen > 0)
+ return -ERANGE;
+ break;
- if (pt->type == NLA_FLAG && nla_len(nla) > 0)
- return -ERANGE;
+ case NLA_NUL_STRING:
+ if (pt->len)
+ minlen = min_t(int, attrlen, pt->len + 1);
+ else
+ minlen = attrlen;
- if (nla_len(nla) < minlen)
- return -ERANGE;
+ if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
+ return -EINVAL;
+ /* fall through */
+
+ case NLA_STRING:
+ if (attrlen < 1)
+ return -ERANGE;
+
+ if (pt->len) {
+ char *buf = nla_data(nla);
+
+ if (buf[attrlen - 1] == '\0')
+ attrlen--;
+
+ if (attrlen > pt->len)
+ return -ERANGE;
+ }
+ break;
+
+ default:
+ if (pt->len)
+ minlen = pt->len;
+ else if (pt->type != NLA_UNSPEC)
+ minlen = nla_attr_minlen[pt->type];
+
+ if (attrlen < minlen)
+ return -ERANGE;
+ }
return 0;
}