[RFC PATCH bpf-next 11/13] bpf: Allow iterating bpf objects with CAP_BPF in bpf namespace

[Yafang Shao <laoar.shao@gmail.com>]

CAP_SYS_ADMIN is not required to iterate bpf objects if a user is in a
non-init bpf namespace. The user can iterate bpf maps, progs, and links
in his bpf namespace but can't iterate the bpf objects in different bpf
namespace.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/linux/bpf_namespace.h |  8 ++++++++
 kernel/bpf/syscall.c          | 10 +++++-----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/include/linux/bpf_namespace.h b/include/linux/bpf_namespace.h
index 50bd68c..f484791 100644
--- a/include/linux/bpf_namespace.h
+++ b/include/linux/bpf_namespace.h
@@ -5,6 +5,7 @@
 #include <linux/idr.h>
 #include <linux/ns_common.h>
 #include <linux/user_namespace.h>
+#include <linux/capability.h>
 
 struct ubpf_obj_id {
 	int nr;
@@ -79,4 +80,11 @@ static inline int bpf_obj_id_vnr(struct bpf_obj_id *obj_id)
 {
 	return bpf_obj_id_nr_ns(obj_id, current->nsproxy->bpf_ns);
 }
+
+static inline bool bpfns_capable(void)
+{
+	if (current->nsproxy->bpf_ns != &init_bpf_ns && capable(CAP_BPF))
+		return true;
+	return false;
+}
 #endif /* _LINUX_BPF_ID_NS_H */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 855d5f7..8a72694 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3628,7 +3628,7 @@ static int bpf_obj_get_next_id(const union bpf_attr *attr,
 	if (CHECK_ATTR(BPF_OBJ_GET_NEXT_ID) || next_id >= INT_MAX)
 		return -EINVAL;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) && !bpfns_capable())
 		return -EPERM;
 
 	next_id++;
@@ -3712,7 +3712,7 @@ static int bpf_prog_get_fd_by_id(const union bpf_attr *attr)
 	if (CHECK_ATTR(BPF_PROG_GET_FD_BY_ID))
 		return -EINVAL;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) && !bpfns_capable())
 		return -EPERM;
 
 	prog = bpf_prog_by_id(id);
@@ -3740,7 +3740,7 @@ static int bpf_map_get_fd_by_id(const union bpf_attr *attr)
 	    attr->open_flags & ~BPF_OBJ_FLAG_MASK)
 		return -EINVAL;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) && !bpfns_capable())
 		return -EPERM;
 
 	f_flags = bpf_get_file_flag(attr->open_flags);
@@ -4386,7 +4386,7 @@ static int bpf_task_fd_query(const union bpf_attr *attr,
 	if (CHECK_ATTR(BPF_TASK_FD_QUERY))
 		return -EINVAL;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) && !bpfns_capable())
 		return -EPERM;
 
 	if (attr->task_fd_query.flags != 0)
@@ -4781,7 +4781,7 @@ static int bpf_link_get_fd_by_id(const union bpf_attr *attr)
 	if (CHECK_ATTR(BPF_LINK_GET_FD_BY_ID))
 		return -EINVAL;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) && !bpfns_capable())
 		return -EPERM;
 
 	link = bpf_link_by_id(id);
-- 
1.8.3.1