bpf: implement BPF_PROG_QUERY for BPF_LSM_CGROUP

We have two options:
1. Treat all BPF_LSM_CGROUP the same, regardless of attach_btf_id
2. Treat BPF_LSM_CGROUP+attach_btf_id as a separate hook point

I was doing (2) in the original patch, but switching to (1) here:

* bpf_prog_query returns all attached BPF_LSM_CGROUP programs
regardless of attach_btf_id
* attach_btf_id is exported via bpf_prog_info

Reviewed-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220628174314.1216643-6-sdf@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index b747989..ad9e731 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1432,6 +1432,7 @@ union bpf_attr {
                __u32           attach_flags;
                __aligned_u64   prog_ids;
                __u32           prog_cnt;
+               __aligned_u64   prog_attach_flags; /* output: per-program attach_flags */
        } query;
 
        struct { /* anonymous struct used by BPF_RAW_TRACEPOINT_OPEN command */
@@ -6076,6 +6077,8 @@ struct bpf_prog_info {
        __u64 run_cnt;
        __u64 recursion_misses;
        __u32 verified_insns;
+       __u32 attach_btf_obj_id;
+       __u32 attach_btf_id;
 } __attribute__((aligned(8)));
 
 struct bpf_map_info {

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 169cbd0..59b7eb6 100644 (file)
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1017,57 +1017,90 @@ static int cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
 static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
                              union bpf_attr __user *uattr)
 {
+       __u32 __user *prog_attach_flags = u64_to_user_ptr(attr->query.prog_attach_flags);
        __u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
        enum bpf_attach_type type = attr->query.attach_type;
+       enum cgroup_bpf_attach_type from_atype, to_atype;
        enum cgroup_bpf_attach_type atype;
        struct bpf_prog_array *effective;
-       struct hlist_head *progs;
-       struct bpf_prog *prog;
        int cnt, ret = 0, i;
+       int total_cnt = 0;
        u32 flags;
 
-       atype = to_cgroup_bpf_attach_type(type);
-       if (atype < 0)
-               return -EINVAL;
-
-       progs = &cgrp->bpf.progs[atype];
-       flags = cgrp->bpf.flags[atype];
+       if (type == BPF_LSM_CGROUP) {
+               if (attr->query.prog_cnt && prog_ids && !prog_attach_flags)
+                       return -EINVAL;
 
-       effective = rcu_dereference_protected(cgrp->bpf.effective[atype],
-                                             lockdep_is_held(&cgroup_mutex));
+               from_atype = CGROUP_LSM_START;
+               to_atype = CGROUP_LSM_END;
+               flags = 0;
+       } else {
+               from_atype = to_cgroup_bpf_attach_type(type);
+               if (from_atype < 0)
+                       return -EINVAL;
+               to_atype = from_atype;
+               flags = cgrp->bpf.flags[from_atype];
+       }
 
-       if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE)
-               cnt = bpf_prog_array_length(effective);
-       else
-               cnt = prog_list_length(progs);
+       for (atype = from_atype; atype <= to_atype; atype++) {
+               if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE) {
+                       effective = rcu_dereference_protected(cgrp->bpf.effective[atype],
+                                                             lockdep_is_held(&cgroup_mutex));
+                       total_cnt += bpf_prog_array_length(effective);
+               } else {
+                       total_cnt += prog_list_length(&cgrp->bpf.progs[atype]);
+               }
+       }
 
        if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
                return -EFAULT;
-       if (copy_to_user(&uattr->query.prog_cnt, &cnt, sizeof(cnt)))
+       if (copy_to_user(&uattr->query.prog_cnt, &total_cnt, sizeof(total_cnt)))
                return -EFAULT;
-       if (attr->query.prog_cnt == 0 || !prog_ids || !cnt)
+       if (attr->query.prog_cnt == 0 || !prog_ids || !total_cnt)
                /* return early if user requested only program count + flags */
                return 0;
-       if (attr->query.prog_cnt < cnt) {
-               cnt = attr->query.prog_cnt;
+
+       if (attr->query.prog_cnt < total_cnt) {
+               total_cnt = attr->query.prog_cnt;
                ret = -ENOSPC;
        }
 
-       if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE) {
-               return bpf_prog_array_copy_to_user(effective, prog_ids, cnt);
-       } else {
-               struct bpf_prog_list *pl;
-               u32 id;
+       for (atype = from_atype; atype <= to_atype && total_cnt; atype++) {
+               if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE) {
+                       effective = rcu_dereference_protected(cgrp->bpf.effective[atype],
+                                                             lockdep_is_held(&cgroup_mutex));
+                       cnt = min_t(int, bpf_prog_array_length(effective), total_cnt);
+                       ret = bpf_prog_array_copy_to_user(effective, prog_ids, cnt);
+               } else {
+                       struct hlist_head *progs;
+                       struct bpf_prog_list *pl;
+                       struct bpf_prog *prog;
+                       u32 id;
+
+                       progs = &cgrp->bpf.progs[atype];
+                       cnt = min_t(int, prog_list_length(progs), total_cnt);
+                       i = 0;
+                       hlist_for_each_entry(pl, progs, node) {
+                               prog = prog_list_prog(pl);
+                               id = prog->aux->id;
+                               if (copy_to_user(prog_ids + i, &id, sizeof(id)))
+                                       return -EFAULT;
+                               if (++i == cnt)
+                                       break;
+                       }
+               }
 
-               i = 0;
-               hlist_for_each_entry(pl, progs, node) {
-                       prog = prog_list_prog(pl);
-                       id = prog->aux->id;
-                       if (copy_to_user(prog_ids + i, &id, sizeof(id)))
-                               return -EFAULT;
-                       if (++i == cnt)
-                               break;
+               if (prog_attach_flags) {
+                       flags = cgrp->bpf.flags[atype];
+
+                       for (i = 0; i < cnt; i++)
+                               if (copy_to_user(prog_attach_flags + i, &flags, sizeof(flags)))
+                                       return -EFAULT;
+                       prog_attach_flags += cnt;
                }
+
+               prog_ids += cnt;
+               total_cnt -= cnt;
        }
        return ret;
 }

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 626b8f7..ab688d8 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3520,7 +3520,7 @@ static int bpf_prog_detach(const union bpf_attr *attr)
        }
 }
 
-#define BPF_PROG_QUERY_LAST_FIELD query.prog_cnt
+#define BPF_PROG_QUERY_LAST_FIELD query.prog_attach_flags
 
 static int bpf_prog_query(const union bpf_attr *attr,
                          union bpf_attr __user *uattr)
@@ -3556,6 +3556,7 @@ static int bpf_prog_query(const union bpf_attr *attr,
        case BPF_CGROUP_SYSCTL:
        case BPF_CGROUP_GETSOCKOPT:
        case BPF_CGROUP_SETSOCKOPT:
+       case BPF_LSM_CGROUP:
                return cgroup_bpf_prog_query(attr, uattr);
        case BPF_LIRC_MODE2:
                return lirc_prog_query(attr, uattr);
@@ -4066,6 +4067,11 @@ static int bpf_prog_get_info_by_fd(struct file *file,
 
        if (prog->aux->btf)
                info.btf_id = btf_obj_id(prog->aux->btf);
+       info.attach_btf_id = prog->aux->attach_btf_id;
+       if (prog->aux->attach_btf)
+               info.attach_btf_obj_id = btf_obj_id(prog->aux->attach_btf);
+       else if (prog->aux->dst_prog)
+               info.attach_btf_obj_id = btf_obj_id(prog->aux->dst_prog->aux->attach_btf);
 
        ulen = info.nr_func_info;
        info.nr_func_info = prog->aux->func_info_cnt;