diff options
authorDavid Ahern <dsahern@gmail.com>2017-12-06 20:09:12 -0800
committerDavid S. Miller <davem@davemloft.net>2017-12-07 14:00:57 -0500
commit6e237d099fac1f73a7b6d7287bb9191f29585a4e (patch)
parent74c4b656c3d92ec4c824ea1a4afd726b7b6568c8 (diff)
netlink: Relax attr validation for fixed length types
Commit 28033ae4e0f5 ("net: netlink: Update attr validation to require exact length for some types") requires attributes using types NLA_U* and NLA_S* to have an exact length. This change is exposing bugs in various userspace commands that are sending attributes with an invalid length (e.g., attribute has type NLA_U8 and userspace sends NLA_U32). While the commands are clearly broken and need to be fixed, users are arguing that the sudden change in enforcement is breaking older commands on newer kernels for use cases that otherwise "worked". Relax the validation to print a warning mesage similar to what is done for messages containing extra bytes after parsing. Fixes: 28033ae4e0f5 ("net: netlink: Update attr validation to require exact length for some types") Signed-off-by: David Ahern <dsahern@gmail.com> Reviewed-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: David S. Miller <davem@davemloft.net>
1 files changed, 16 insertions, 6 deletions
diff --git a/lib/nlattr.c b/lib/nlattr.c
index 8bf78b4b78f0..dfa55c873c13 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -15,7 +15,11 @@
#include <linux/types.h>
#include <net/netlink.h>
-/* for these data types attribute length must be exactly given size */
+/* For these data types, attribute length should be exactly the given
+ * size. However, to maintain compatibility with broken commands, if the
+ * attribute length does not match the expected size a warning is emitted
+ * to the user that the command is sending invalid data and needs to be fixed.
+ */
static const u8 nla_attr_len[NLA_TYPE_MAX+1] = {
[NLA_U8] = sizeof(u8),
[NLA_U16] = sizeof(u16),
@@ -28,8 +32,16 @@ static const u8 nla_attr_len[NLA_TYPE_MAX+1] = {
static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = {
+ [NLA_U8] = sizeof(u8),
+ [NLA_U16] = sizeof(u16),
+ [NLA_U32] = sizeof(u32),
+ [NLA_U64] = sizeof(u64),
[NLA_MSECS] = sizeof(u64),
+ [NLA_S8] = sizeof(s8),
+ [NLA_S16] = sizeof(s16),
+ [NLA_S32] = sizeof(s32),
+ [NLA_S64] = sizeof(s64),
static int validate_nla_bitfield32(const struct nlattr *nla,
@@ -69,11 +81,9 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
BUG_ON(pt->type > NLA_TYPE_MAX);
- /* for data types NLA_U* and NLA_S* require exact length */
- if (nla_attr_len[pt->type]) {
- if (attrlen != nla_attr_len[pt->type])
- return -ERANGE;
- return 0;
+ if (nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) {
+ pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
+ current->comm, type);
switch (pt->type) {