From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Making this work is a little tricky as it really isn't kosher to change the xt_owner_match_info in a check function. Without changing xt_owner_match_info we need to know the user namespace the uids and gids are specified in. In the common case net->user_ns == current_user_ns(). Verify net->user_ns == current_user_ns() in owner_check so we can later assume it in owner_mt. In owner_check also verify that all of the uids and gids specified are in net->user_ns and that the expected min/max relationship exists between the uids and gids in xt_owner_match_info. In owner_mt get the network namespace from the outgoing socket, as this must be the same network namespace as the netfilter rules, and use that network namespace to find the user namespace the uids and gids in xt_match_owner_info are encoded in. Then convert from their encoded from into the kernel internal format for uids and gids and perform the owner match. Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Signed-off-by: Kevin Cernekee <cernekee@xxxxxxxxxxxx> --- Original post: https://lists.linuxfoundation.org/pipermail/containers/2014-May/034514.html V1->V2: - Change (max <= min) check to (max < min), because it is legal for min == max. I suspect this was the root cause of this error: https://lists.linuxfoundation.org/pipermail/containers/2014-June/034661.html - Fix checkpatch warnings. This was tested on a system running Linux 3.14, then compile-tested on Linus' master branch. Similar to ping_group_range, this code does not try to detect noncontiguous UID/GID ranges. net/netfilter/xt_owner.c | 42 ++++++++++++++++++++++++++++++++++++------ 1 file changed, 36 insertions(+), 6 deletions(-) diff --git a/net/netfilter/xt_owner.c b/net/netfilter/xt_owner.c index 1302b475abcb..e1c1f31ef1e9 100644 --- a/net/netfilter/xt_owner.c +++ b/net/netfilter/xt_owner.c @@ -21,11 +21,39 @@ static int owner_check(const struct xt_mtchk_param *par) { struct xt_owner_match_info *info = par->matchinfo; + struct net *net = par->net; - /* For now only allow adding matches from the initial user namespace */ + /* Only allow the common case where the userns of the writer + * matches the userns of the network namespace. + */ if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) && - (current_user_ns() != &init_user_ns)) + (current_user_ns() != net->user_ns)) return -EINVAL; + + /* Ensure the uids are valid */ + if (info->match & XT_OWNER_UID) { + kuid_t uid_min = make_kuid(net->user_ns, info->uid_min); + kuid_t uid_max = make_kuid(net->user_ns, info->uid_max); + + if (!uid_valid(uid_min) || !uid_valid(uid_max) || + (info->uid_max < info->uid_min) || + uid_lt(uid_max, uid_min)) { + return -EINVAL; + } + } + + /* Ensure the gids are valid */ + if (info->match & XT_OWNER_GID) { + kgid_t gid_min = make_kgid(net->user_ns, info->gid_min); + kgid_t gid_max = make_kgid(net->user_ns, info->gid_max); + + if (!gid_valid(gid_min) || !gid_valid(gid_max) || + (info->gid_max < info->gid_min) || + gid_lt(gid_max, gid_min)) { + return -EINVAL; + } + } + return 0; } @@ -35,6 +63,7 @@ owner_mt(const struct sk_buff *skb, struct xt_action_param *par) const struct xt_owner_match_info *info = par->matchinfo; const struct file *filp; struct sock *sk = skb_to_full_sk(skb); + const struct net *net; if (sk == NULL || sk->sk_socket == NULL) return (info->match ^ info->invert) == 0; @@ -50,9 +79,10 @@ owner_mt(const struct sk_buff *skb, struct xt_action_param *par) return ((info->match ^ info->invert) & (XT_OWNER_UID | XT_OWNER_GID)) == 0; + net = sock_net(skb->sk); if (info->match & XT_OWNER_UID) { - kuid_t uid_min = make_kuid(&init_user_ns, info->uid_min); - kuid_t uid_max = make_kuid(&init_user_ns, info->uid_max); + kuid_t uid_min = make_kuid(net->user_ns, info->uid_min); + kuid_t uid_max = make_kuid(net->user_ns, info->uid_max); if ((uid_gte(filp->f_cred->fsuid, uid_min) && uid_lte(filp->f_cred->fsuid, uid_max)) ^ !(info->invert & XT_OWNER_UID)) @@ -60,8 +90,8 @@ owner_mt(const struct sk_buff *skb, struct xt_action_param *par) } if (info->match & XT_OWNER_GID) { - kgid_t gid_min = make_kgid(&init_user_ns, info->gid_min); - kgid_t gid_max = make_kgid(&init_user_ns, info->gid_max); + kgid_t gid_min = make_kgid(net->user_ns, info->gid_min); + kgid_t gid_max = make_kgid(net->user_ns, info->gid_max); if ((gid_gte(filp->f_cred->fsgid, gid_min) && gid_lte(filp->f_cred->fsgid, gid_max)) ^ !(info->invert & XT_OWNER_GID)) -- 2.8.0.rc3.226.g39d4020 -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
