diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h index 0cf1adfadd2d..ace92fce296d 100644 --- a/include/linux/bpf-cgroup.h +++ b/include/linux/bpf-cgroup.h @@ -21,20 +21,19 @@ struct cgroup_bpf { */ struct bpf_prog *prog[MAX_BPF_ATTACH_TYPE]; struct bpf_prog *effective[MAX_BPF_ATTACH_TYPE]; + bool disallow_override[MAX_BPF_ATTACH_TYPE]; }; void cgroup_bpf_put(struct cgroup *cgrp); void cgroup_bpf_inherit(struct cgroup *cgrp, struct cgroup *parent); -void __cgroup_bpf_update(struct cgroup *cgrp, - struct cgroup *parent, - struct bpf_prog *prog, - enum bpf_attach_type type); +int __cgroup_bpf_update(struct cgroup *cgrp, struct cgroup *parent, + struct bpf_prog *prog, enum bpf_attach_type type, + bool overridable); /* Wrapper for __cgroup_bpf_update() protected by cgroup_mutex */ -void cgroup_bpf_update(struct cgroup *cgrp, - struct bpf_prog *prog, - enum bpf_attach_type type); +int cgroup_bpf_update(struct cgroup *cgrp, struct bpf_prog *prog, + enum bpf_attach_type type, bool overridable); int __cgroup_bpf_run_filter(struct sock *sk, struct sk_buff *skb, diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 14eaf2d5ec13..b2d5be9fc909 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -109,6 +109,12 @@ enum bpf_attach_type { #define MAX_BPF_ATTACH_TYPE __MAX_BPF_ATTACH_TYPE +/* If BPF_F_ALLOW_OVERRIDE flag is used in BPF_PROG_ATTACH command + * to the given target_fd cgroup the descendent cgroup will be able to + * override effective bpf program that was inherited from this cgroup + */ +#define BPF_F_ALLOW_OVERRIDE (1U << 0) + #define BPF_PSEUDO_MAP_FD 1 /* flags for BPF_MAP_UPDATE_ELEM command */ @@ -157,6 +163,7 @@ union bpf_attr { __u32 target_fd; /* container object to attach to */ __u32 attach_bpf_fd; /* eBPF program to attach */ __u32 attach_type; + __u32 attach_flags; }; } __attribute__((aligned(8))); diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index d05c292290fe..a38d7cdb5ef8 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -52,6 +52,7 @@ void cgroup_bpf_inherit(struct cgroup *cgrp, struct cgroup *parent) e = rcu_dereference_protected(parent->bpf.effective[type], lockdep_is_held(&cgroup_mutex)); rcu_assign_pointer(cgrp->bpf.effective[type], e); + cgrp->bpf.disallow_override[type] = parent->bpf.disallow_override[type]; } } @@ -82,30 +83,63 @@ void cgroup_bpf_inherit(struct cgroup *cgrp, struct cgroup *parent) * * Must be called with cgroup_mutex held. */ -void __cgroup_bpf_update(struct cgroup *cgrp, - struct cgroup *parent, - struct bpf_prog *prog, - enum bpf_attach_type type) +int __cgroup_bpf_update(struct cgroup *cgrp, struct cgroup *parent, + struct bpf_prog *prog, enum bpf_attach_type type, + bool new_overridable) { - struct bpf_prog *old_prog, *effective; + struct bpf_prog *old_prog, *effective = NULL; struct cgroup_subsys_state *pos; + bool overridable = true; - old_prog = xchg(cgrp->bpf.prog + type, prog); + if (parent) { + overridable = !parent->bpf.disallow_override[type]; + effective = rcu_dereference_protected(parent->bpf.effective[type], + lockdep_is_held(&cgroup_mutex)); + } - effective = (!prog && parent) ? - rcu_dereference_protected(parent->bpf.effective[type], - lockdep_is_held(&cgroup_mutex)) : - prog; + if (prog && effective && !overridable) + /* if parent has non-overridable prog attached, disallow + * attaching new programs to descendent cgroup + */ + return -EPERM; + + if (prog && effective && overridable != new_overridable) + /* if parent has overridable prog attached, only + * allow overridable programs in descendent cgroup + */ + return -EPERM; + + old_prog = cgrp->bpf.prog[type]; + + if (prog) { + overridable = new_overridable; + effective = prog; + if (old_prog && + cgrp->bpf.disallow_override[type] == new_overridable) + /* disallow attaching non-overridable on top + * of existing overridable in this cgroup + * and vice versa + */ + return -EPERM; + } + + if (!prog && !old_prog) + /* report error when trying to detach and nothing is attached */ + return -ENOENT; + + cgrp->bpf.prog[type] = prog; css_for_each_descendant_pre(pos, &cgrp->self) { struct cgroup *desc = container_of(pos, struct cgroup, self); /* skip the subtree if the descendant has its own program */ - if (desc->bpf.prog[type] && desc != cgrp) + if (desc->bpf.prog[type] && desc != cgrp) { pos = css_rightmost_descendant(pos); - else + } else { rcu_assign_pointer(desc->bpf.effective[type], effective); + desc->bpf.disallow_override[type] = !overridable; + } } if (prog) @@ -115,6 +149,7 @@ 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 e13157fd4253..9ab04796bce0 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -826,12 +826,13 @@ static int bpf_obj_get(const union bpf_attr *attr) #ifdef CONFIG_CGROUP_BPF -#define BPF_PROG_ATTACH_LAST_FIELD attach_type +#define BPF_PROG_ATTACH_LAST_FIELD attach_flags static int bpf_prog_attach(const union bpf_attr *attr) { struct bpf_prog *prog; struct cgroup *cgrp; + int ret; if (!capable(CAP_NET_ADMIN)) return -EPERM; @@ -839,6 +840,9 @@ static int bpf_prog_attach(const union bpf_attr *attr) if (CHECK_ATTR(BPF_PROG_ATTACH)) return -EINVAL; + if (attr->attach_flags & ~BPF_F_ALLOW_OVERRIDE) + return -EINVAL; + switch (attr->attach_type) { case BPF_CGROUP_INET_INGRESS: case BPF_CGROUP_INET_EGRESS: @@ -853,7 +857,10 @@ static int bpf_prog_attach(const union bpf_attr *attr) return PTR_ERR(cgrp); } - cgroup_bpf_update(cgrp, prog, attr->attach_type); + ret = cgroup_bpf_update(cgrp, prog, attr->attach_type, + attr->attach_flags & BPF_F_ALLOW_OVERRIDE); + if (ret) + bpf_prog_put(prog); cgroup_put(cgrp); break; @@ -861,7 +868,7 @@ static int bpf_prog_attach(const union bpf_attr *attr) return -EINVAL; } - return 0; + return ret; } #define BPF_PROG_DETACH_LAST_FIELD attach_type @@ -869,6 +876,7 @@ static int bpf_prog_attach(const union bpf_attr *attr) static int bpf_prog_detach(const union bpf_attr *attr) { struct cgroup *cgrp; + int ret; if (!capable(CAP_NET_ADMIN)) return -EPERM; @@ -883,7 +891,7 @@ 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); + ret = cgroup_bpf_update(cgrp, NULL, attr->attach_type, false); cgroup_put(cgrp); break; @@ -891,7 +899,7 @@ static int bpf_prog_detach(const union bpf_attr *attr) return -EINVAL; } - return 0; + return ret; } #endif /* CONFIG_CGROUP_BPF */ diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 70e1f486a0b3..5671c805842d 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -6500,15 +6500,16 @@ static __init int cgroup_namespaces_init(void) subsys_initcall(cgroup_namespaces_init); #ifdef CONFIG_CGROUP_BPF -void cgroup_bpf_update(struct cgroup *cgrp, - struct bpf_prog *prog, - enum bpf_attach_type type) +int cgroup_bpf_update(struct cgroup *cgrp, struct bpf_prog *prog, + enum bpf_attach_type type, bool overridable) { struct cgroup *parent = cgroup_parent(cgrp); + int ret; mutex_lock(&cgroup_mutex); - __cgroup_bpf_update(cgrp, parent, prog, type); + ret = __cgroup_bpf_update(cgrp, parent, prog, type, overridable); mutex_unlock(&cgroup_mutex); + return ret; } #endif /* CONFIG_CGROUP_BPF */ diff --git a/samples/bpf/libbpf.c b/samples/bpf/libbpf.c index 9ce707bf02a7..9cbc786e48e5 100644 --- a/samples/bpf/libbpf.c +++ b/samples/bpf/libbpf.c @@ -104,12 +104,14 @@ int bpf_prog_load(enum bpf_prog_type prog_type, return syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr)); } -int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type) +int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type, + unsigned int flags) { union bpf_attr attr = { .target_fd = target_fd, .attach_bpf_fd = prog_fd, .attach_type = type, + .attach_flags = flags; }; return syscall(__NR_bpf, BPF_PROG_ATTACH, &attr, sizeof(attr)); diff --git a/samples/bpf/libbpf.h b/samples/bpf/libbpf.h index d0a799a52eaf..b06cf5aea097 100644 --- a/samples/bpf/libbpf.h +++ b/samples/bpf/libbpf.h @@ -15,7 +15,8 @@ int bpf_prog_load(enum bpf_prog_type prog_type, const struct bpf_insn *insns, int insn_len, const char *license, int kern_version); -int bpf_prog_attach(int prog_fd, int attachable_fd, enum bpf_attach_type type); +int bpf_prog_attach(int prog_fd, int attachable_fd, enum bpf_attach_type type, + unsigned int flags); int bpf_prog_detach(int attachable_fd, enum bpf_attach_type type); int bpf_obj_pin(int fd, const char *pathname); diff --git a/samples/bpf/test_cgrp2_attach.c b/samples/bpf/test_cgrp2_attach.c index 63ef2083f766..9de4896edeef 100644 --- a/samples/bpf/test_cgrp2_attach.c +++ b/samples/bpf/test_cgrp2_attach.c @@ -124,7 +124,7 @@ int main(int argc, char **argv) ret = bpf_prog_detach(cg_fd, type); printf("bpf_prog_detach() returned '%s' (%d)\n", strerror(errno), errno); - ret = bpf_prog_attach(prog_fd, cg_fd, type); + ret = bpf_prog_attach(prog_fd, cg_fd, type, 0); if (ret < 0) { printf("Failed to attach prog to cgroup: '%s'\n", strerror(errno));