From: Johannes Berg <johannes.berg@xxxxxxxxx>
Commonly, ethernet addresses are just using a policy of
{ .len = ETH_ALEN }
which leaves userspace free to send more data than it should,
which may hide bugs.
Introduce NLA_ETH_ADDR which checks for exact size, and rejects
the attribute if the length isn't ETH_ALEN.
Also add NLA_ETH_ADDR_COMPAT which can be used in place of the
pure length policy, but will, in addition, trigger a netlink
attribute warning if the passed value is too long.
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
include/net/netlink.h | 4 ++++
lib/nlattr.c | 8 ++++++++
2 files changed, 12 insertions(+)
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 04e40fcc70d6..1139163c0db0 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -181,6 +181,8 @@ enum {
NLA_S64,
NLA_BITFIELD32,
NLA_REJECT,
+ NLA_ETH_ADDR,
+ NLA_ETH_ADDR_COMPAT,
__NLA_TYPE_MAX,
};
@@ -213,6 +215,8 @@ enum {
* data must point to a u32 value of valid flags
* NLA_REJECT Reject this attribute, validation data may point
* to a string to report as the error in extended ACK.
+ * NLA_ETH_ADDR Ethernet address, rejected if not exactly 6 octets.
+ * NLA_ETH_ADDR_COMPAT Ethernet address, only warns if not exactly 6 octets.
* All other Minimum length of attribute payload
*
* Example:
diff --git a/lib/nlattr.c b/lib/nlattr.c
index 56e0aae5cf23..b7c519f6e12a 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -29,6 +29,8 @@ static const u8 nla_attr_len[NLA_TYPE_MAX+1] = {
[NLA_S16] = sizeof(s16),
[NLA_S32] = sizeof(s32),
[NLA_S64] = sizeof(s64),
+ [NLA_ETH_ADDR] = ETH_ALEN,
+ [NLA_ETH_ADDR_COMPAT] = ETH_ALEN,
};
static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = {
@@ -42,6 +44,7 @@ static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = {
[NLA_S16] = sizeof(s16),
[NLA_S32] = sizeof(s32),
[NLA_S64] = sizeof(s64),
+ [NLA_ETH_ADDR_COMPAT] = ETH_ALEN,
};
static int validate_nla_bitfield32(const struct nlattr *nla,
@@ -93,6 +96,11 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
extack->_msg = pt->validation_data;
return -EINVAL;
+ case NLA_ETH_ADDR:
+ if (attrlen != ETH_ALEN)
+ return -ERANGE;
+ break;
+
case NLA_FLAG:
if (attrlen > 0)
return -ERANGE;
--
2.14.4
