[kernel-hardening] [RFC v4 14/18] bpf/cgroup: Make cgroup_bpf_update() return an error code

["Mickaël Salaün" <mic@digikod.net>]

This will be useful to support Landlock for the next commits.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Daniel Mack <daniel@zonque.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Tejun Heo <tj@kernel.org>
---
 include/linux/bpf-cgroup.h |  4 ++--
 kernel/bpf/cgroup.c        |  3 ++-
 kernel/bpf/syscall.c       | 10 ++++++----
 kernel/cgroup.c            |  6 ++++--
 4 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index 2f608e5d94e9..aab1aa91c064 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -31,13 +31,13 @@ struct cgroup_bpf {
 void cgroup_bpf_put(struct cgroup *cgrp);
 void cgroup_bpf_inherit(struct cgroup *cgrp, struct cgroup *parent);
 
-void __cgroup_bpf_update(struct cgroup *cgrp,
+int __cgroup_bpf_update(struct cgroup *cgrp,
 			 struct cgroup *parent,
 			 struct bpf_prog *prog,
 			 enum bpf_attach_type type);
 
 /* Wrapper for __cgroup_bpf_update() protected by cgroup_mutex */
-void cgroup_bpf_update(struct cgroup *cgrp,
+int cgroup_bpf_update(struct cgroup *cgrp,
 		       struct bpf_prog *prog,
 		       enum bpf_attach_type type);
 
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 75482cd92d56..269b410d890c 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -83,7 +83,7 @@ void cgroup_bpf_inherit(struct cgroup *cgrp, struct cgroup *parent)
  *
  * Must be called with cgroup_mutex held.
  */
-void __cgroup_bpf_update(struct cgroup *cgrp,
+int __cgroup_bpf_update(struct cgroup *cgrp,
 			 struct cgroup *parent,
 			 struct bpf_prog *prog,
 			 enum bpf_attach_type type)
@@ -116,6 +116,7 @@ void __cgroup_bpf_update(struct cgroup *cgrp,
 		bpf_prog_put(old_prog);
 		static_branch_dec(&cgroup_bpf_enabled_key);
 	}
+	return 0;
 }
 
 /**
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index ac4cbb98596d..e62123aeb202 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -831,6 +831,7 @@ static int bpf_prog_attach(const union bpf_attr *attr)
 {
 	struct bpf_prog *prog;
 	struct cgroup *cgrp;
+	int result;
 
 	if (!capable(CAP_NET_ADMIN))
 		return -EPERM;
@@ -858,10 +859,10 @@ static int bpf_prog_attach(const union bpf_attr *attr)
 		return PTR_ERR(cgrp);
 	}
 
-	cgroup_bpf_update(cgrp, prog, attr->attach_type);
+	result = cgroup_bpf_update(cgrp, prog, attr->attach_type);
 	cgroup_put(cgrp);
 
-	return 0;
+	return result;
 }
 
 #define BPF_PROG_DETACH_LAST_FIELD attach_type
@@ -869,6 +870,7 @@ static int bpf_prog_attach(const union bpf_attr *attr)
 static int bpf_prog_detach(const union bpf_attr *attr)
 {
 	struct cgroup *cgrp;
+	int result = 0;
 
 	if (!capable(CAP_NET_ADMIN))
 		return -EPERM;
@@ -883,7 +885,7 @@ static int bpf_prog_detach(const union bpf_attr *attr)
 		if (IS_ERR(cgrp))
 			return PTR_ERR(cgrp);
 
-		cgroup_bpf_update(cgrp, NULL, attr->attach_type);
+		result = cgroup_bpf_update(cgrp, NULL, attr->attach_type);
 		cgroup_put(cgrp);
 		break;
 
@@ -891,7 +893,7 @@ static int bpf_prog_detach(const union bpf_attr *attr)
 		return -EINVAL;
 	}
 
-	return 0;
+	return result;
 }
 #endif /* CONFIG_CGROUP_BPF */
 
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2ee9ec3051b2..f77a974eb960 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -6501,15 +6501,17 @@ static __init int cgroup_namespaces_init(void)
 subsys_initcall(cgroup_namespaces_init);
 
 #ifdef CONFIG_CGROUP_BPF
-void cgroup_bpf_update(struct cgroup *cgrp,
+int cgroup_bpf_update(struct cgroup *cgrp,
 		       struct bpf_prog *prog,
 		       enum bpf_attach_type type)
 {
 	struct cgroup *parent = cgroup_parent(cgrp);
+	int result;
 
 	mutex_lock(&cgroup_mutex);
-	__cgroup_bpf_update(cgrp, parent, prog, type);
+	result = __cgroup_bpf_update(cgrp, parent, prog, type);
 	mutex_unlock(&cgroup_mutex);
+	return result;
 }
 #endif /* CONFIG_CGROUP_BPF */
 
-- 
2.9.3