From: David Ahern <dsah...@gmail.com>
Date: Tue, 5 Dec 2017 12:55:40 -0700
> 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 <dsah...@gmail.com>
Johannes, please review.
> ---
> lib/nlattr.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/lib/nlattr.c b/lib/nlattr.c
> index 8bf78b4b78f0..6122662906c8 100644
> --- a/lib/nlattr.c
> +++ b/lib/nlattr.c
> @@ -28,8 +28,16 @@ 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_NESTED] = NLA_HDRLEN,
> + [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,
> @@ -70,10 +78,9 @@ 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) {
> --
> 2.11.0
>
