bpf: flow_dissector: Check value of unused flags to BPF_PROG_DETACH

Using BPF_PROG_DETACH on a flow dissector program supports neither
attach_flags nor attach_bpf_fd. Yet no value is enforced for them.

Enforce that attach_flags are zero, and require the current program
to be passed via attach_bpf_fd. This allows us to remove the check
for CAP_SYS_ADMIN, since userspace can now no longer remove
arbitrary flow dissector programs.

Fixes: 52cd61d23445 ("flow_dissector: Move out netns_bpf prog callbacks")
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200629095630.7933-3-lmb@cloudflare.com

diff --git a/include/linux/bpf-netns.h b/include/linux/bpf-netns.h
index 4052d649f36d05d732bd69d8ca784ac2be3b1275..47d5b0c708c98bffcbad9a915725be64b7809139 100644 (file)
--- a/include/linux/bpf-netns.h
+++ b/include/linux/bpf-netns.h
@@ -33,7 +33,7 @@ int netns_bpf_prog_query(const union bpf_attr *attr,
                         union bpf_attr __user *uattr);
 int netns_bpf_prog_attach(const union bpf_attr *attr,
                          struct bpf_prog *prog);
-int netns_bpf_prog_detach(const union bpf_attr *attr);
+int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype);
 int netns_bpf_link_create(const union bpf_attr *attr,
                          struct bpf_prog *prog);
 #else
@@ -49,7 +49,8 @@ static inline int netns_bpf_prog_attach(const union bpf_attr *attr,
        return -EOPNOTSUPP;
 }
 
-static inline int netns_bpf_prog_detach(const union bpf_attr *attr)
+static inline int netns_bpf_prog_detach(const union bpf_attr *attr,
+                                       enum bpf_prog_type ptype)
 {
        return -EOPNOTSUPP;
 }

diff --git a/kernel/bpf/net_namespace.c b/kernel/bpf/net_namespace.c
index 03045f45afec8c13ae41de892ea52b8aad30dc43..3dbc29b6f51d2792a17cd5262652d6fc5cf28bdc 100644 (file)
--- a/kernel/bpf/net_namespace.c
+++ b/kernel/bpf/net_namespace.c
@@ -269,7 +269,8 @@ out_unlock:
 
 /* Must be called with netns_bpf_mutex held. */
 static int __netns_bpf_prog_detach(struct net *net,
-                                  enum netns_bpf_attach_type type)
+                                  enum netns_bpf_attach_type type,
+                                  struct bpf_prog *old)
 {
        struct bpf_prog *attached;
 
@@ -278,7 +279,7 @@ static int __netns_bpf_prog_detach(struct net *net,
                return -EINVAL;
 
        attached = net->bpf.progs[type];
-       if (!attached)
+       if (!attached || attached != old)
                return -ENOENT;
        netns_bpf_run_array_detach(net, type);
        net->bpf.progs[type] = NULL;
@@ -286,19 +287,29 @@ static int __netns_bpf_prog_detach(struct net *net,
        return 0;
 }
 
-int netns_bpf_prog_detach(const union bpf_attr *attr)
+int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
 {
        enum netns_bpf_attach_type type;
+       struct bpf_prog *prog;
        int ret;
 
+       if (attr->target_fd)
+               return -EINVAL;
+
        type = to_netns_bpf_attach_type(attr->attach_type);
        if (type < 0)
                return -EINVAL;
 
+       prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
+       if (IS_ERR(prog))
+               return PTR_ERR(prog);
+
        mutex_lock(&netns_bpf_mutex);
-       ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type);
+       ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type, prog);
        mutex_unlock(&netns_bpf_mutex);
 
+       bpf_prog_put(prog);
+
        return ret;
 }
 

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 7d946435587dea8ceb5a06ddad23279d0279030c..28c6ef7590370af7bc075deca251182f7bf2f618 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2897,9 +2897,7 @@ static int bpf_prog_detach(const union bpf_attr *attr)
        case BPF_PROG_TYPE_LIRC_MODE2:
                return lirc_prog_detach(attr);
        case BPF_PROG_TYPE_FLOW_DISSECTOR:
-               if (!capable(CAP_NET_ADMIN))
-                       return -EPERM;
-               return netns_bpf_prog_detach(attr);
+               return netns_bpf_prog_detach(attr, ptype);
        case BPF_PROG_TYPE_CGROUP_DEVICE:
        case BPF_PROG_TYPE_CGROUP_SKB:
        case BPF_PROG_TYPE_CGROUP_SOCK: