bpf: Refactor bpf_link update handling

Make bpf_link update support more generic by making it into another
bpf_link_ops methods. This allows generic syscall handling code to be agnostic
to various conditionally compiled features (e.g., the case of
CONFIG_CGROUP_BPF). This also allows to keep link type-specific code to remain
static within respective code base. Refactor existing bpf_cgroup_link code and
take advantage of this.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200429001614.1544-2-andriin@fb.com

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index 0b41fd5..a9cb9a5 100644 (file)
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -100,8 +100,6 @@ int __cgroup_bpf_attach(struct cgroup *cgrp,
 int __cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
                        struct bpf_cgroup_link *link,
                        enum bpf_attach_type type);
-int __cgroup_bpf_replace(struct cgroup *cgrp, struct bpf_cgroup_link *link,
-                        struct bpf_prog *new_prog);
 int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
                       union bpf_attr __user *uattr);
 
@@ -112,8 +110,6 @@ int cgroup_bpf_attach(struct cgroup *cgrp,
                      u32 flags);
 int cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
                      enum bpf_attach_type type);
-int cgroup_bpf_replace(struct bpf_link *link, struct bpf_prog *old_prog,
-                      struct bpf_prog *new_prog);
 int cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
                     union bpf_attr __user *uattr);
 
@@ -353,7 +349,6 @@ int cgroup_bpf_prog_query(const union bpf_attr *attr,
 #else
 
 struct bpf_prog;
-struct bpf_link;
 struct cgroup_bpf {};
 static inline int cgroup_bpf_inherit(struct cgroup *cgrp) { return 0; }
 static inline void cgroup_bpf_offline(struct cgroup *cgrp) {}
@@ -377,13 +372,6 @@ static inline int cgroup_bpf_link_attach(const union bpf_attr *attr,
        return -EINVAL;
 }
 
-static inline int cgroup_bpf_replace(struct bpf_link *link,
-                                    struct bpf_prog *old_prog,
-                                    struct bpf_prog *new_prog)
-{
-       return -EINVAL;
-}
-
 static inline int cgroup_bpf_prog_query(const union bpf_attr *attr,
                                        union bpf_attr __user *uattr)
 {

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 10960cf..81c8620 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1093,7 +1093,8 @@ struct bpf_link {
 struct bpf_link_ops {
        void (*release)(struct bpf_link *link);
        void (*dealloc)(struct bpf_link *link);
-
+       int (*update_prog)(struct bpf_link *link, struct bpf_prog *new_prog,
+                          struct bpf_prog *old_prog);
 };
 
 void bpf_link_init(struct bpf_link *link, const struct bpf_link_ops *ops,

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index bf63495..da6e48e 100644 (file)
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -557,8 +557,9 @@ found:
  *
  * Must be called with cgroup_mutex held.
  */
-int __cgroup_bpf_replace(struct cgroup *cgrp, struct bpf_cgroup_link *link,
-                        struct bpf_prog *new_prog)
+static int __cgroup_bpf_replace(struct cgroup *cgrp,
+                               struct bpf_cgroup_link *link,
+                               struct bpf_prog *new_prog)
 {
        struct list_head *progs = &cgrp->bpf.progs[link->type];
        struct bpf_prog *old_prog;
@@ -583,6 +584,30 @@ int __cgroup_bpf_replace(struct cgroup *cgrp, struct bpf_cgroup_link *link,
        return 0;
 }
 
+static int cgroup_bpf_replace(struct bpf_link *link, struct bpf_prog *new_prog,
+                             struct bpf_prog *old_prog)
+{
+       struct bpf_cgroup_link *cg_link;
+       int ret;
+
+       cg_link = container_of(link, struct bpf_cgroup_link, link);
+
+       mutex_lock(&cgroup_mutex);
+       /* link might have been auto-released by dying cgroup, so fail */
+       if (!cg_link->cgroup) {
+               ret = -EINVAL;
+               goto out_unlock;
+       }
+       if (old_prog && link->prog != old_prog) {
+               ret = -EPERM;
+               goto out_unlock;
+       }
+       ret = __cgroup_bpf_replace(cg_link->cgroup, cg_link, new_prog);
+out_unlock:
+       mutex_unlock(&cgroup_mutex);
+       return ret;
+}
+
 static struct bpf_prog_list *find_detach_entry(struct list_head *progs,
                                               struct bpf_prog *prog,
                                               struct bpf_cgroup_link *link,
@@ -811,6 +836,7 @@ static void bpf_cgroup_link_dealloc(struct bpf_link *link)
 const struct bpf_link_ops bpf_cgroup_link_lops = {
        .release = bpf_cgroup_link_release,
        .dealloc = bpf_cgroup_link_dealloc,
+       .update_prog = cgroup_bpf_replace,
 };
 
 int cgroup_bpf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 7626b80..f5358e1 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3645,13 +3645,10 @@ static int link_update(union bpf_attr *attr)
                goto out_put_progs;
        }
 
-#ifdef CONFIG_CGROUP_BPF
-       if (link->ops == &bpf_cgroup_link_lops) {
-               ret = cgroup_bpf_replace(link, old_prog, new_prog);
-               goto out_put_progs;
-       }
-#endif
-       ret = -EINVAL;
+       if (link->ops->update_prog)
+               ret = link->ops->update_prog(link, new_prog, old_prog);
+       else
+               ret = EINVAL;
 
 out_put_progs:
        if (old_prog)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 06b5ea9..557a9b9 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -6508,33 +6508,6 @@ int cgroup_bpf_attach(struct cgroup *cgrp,
        return ret;
 }
 
-int cgroup_bpf_replace(struct bpf_link *link, struct bpf_prog *old_prog,
-                      struct bpf_prog *new_prog)
-{
-       struct bpf_cgroup_link *cg_link;
-       int ret;
-
-       if (link->ops != &bpf_cgroup_link_lops)
-               return -EINVAL;
-
-       cg_link = container_of(link, struct bpf_cgroup_link, link);
-
-       mutex_lock(&cgroup_mutex);
-       /* link might have been auto-released by dying cgroup, so fail */
-       if (!cg_link->cgroup) {
-               ret = -EINVAL;
-               goto out_unlock;
-       }
-       if (old_prog && link->prog != old_prog) {
-               ret = -EPERM;
-               goto out_unlock;
-       }
-       ret = __cgroup_bpf_replace(cg_link->cgroup, cg_link, new_prog);
-out_unlock:
-       mutex_unlock(&cgroup_mutex);
-       return ret;
-}
-
 int cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
                      enum bpf_attach_type type)
 {