A previous commit expanded the usage scope of bpf_get_cgroup_classid() to all contexts (see Fixes tag), but this was inappropriate.
First, syzkaller reported a bug [1]. Second, it uses skb as an argument, but its implementation varies across different bpf prog types. For example, in sock_filter and sock_addr, it retrieves the classid from the current context (bpf_get_cgroup_classid_curr_proto) instead of from skb. In tc egress and lwt, it fetches the classid from skb->sk, but in tc ingress, it returns 0. In summary, the definition of bpf_get_cgroup_classid() is ambiguous and its usage scenarios are limited. It should not be treated as a general-purpose helper. This patch reverts part of the previous commit. [1] https://syzkaller.appspot.com/bug?extid=9767c7ed68b95cfa69e6 Fixes: ee971630f20f ("bpf: Allow some trace helpers for all prog types") Reported-by: syzbot+9767c7ed68b95cfa6...@syzkaller.appspotmail.com Signed-off-by: Jiayuan Chen <jiayuan.c...@linux.dev> --- include/linux/bpf-cgroup.h | 8 ++++++++ kernel/bpf/cgroup.c | 25 +++++++++++++++++++++++++ kernel/bpf/helpers.c | 4 ---- 3 files changed, 33 insertions(+), 4 deletions(-) diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h index 4847dcade917..9de7adb68294 100644 --- a/include/linux/bpf-cgroup.h +++ b/include/linux/bpf-cgroup.h @@ -427,6 +427,8 @@ int cgroup_bpf_prog_query(const union bpf_attr *attr, const struct bpf_func_proto * cgroup_common_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog); +const struct bpf_func_proto * +cgroup_current_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog); #else static inline int cgroup_bpf_inherit(struct cgroup *cgrp) { return 0; } @@ -463,6 +465,12 @@ cgroup_common_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return NULL; } +static inline const struct bpf_func_proto * +cgroup_current_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) +{ + return NULL; +} + static inline int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux, struct bpf_map *map) { return 0; } static inline struct bpf_cgroup_storage *bpf_cgroup_storage_alloc( diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 62a1d8deb3dc..a99b72e6f1c9 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1653,6 +1653,10 @@ cgroup_dev_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) if (func_proto) return func_proto; + func_proto = cgroup_current_func_proto(func_id, prog); + if (func_proto) + return func_proto; + switch (func_id) { case BPF_FUNC_perf_event_output: return &bpf_event_output_data_proto; @@ -2200,6 +2204,10 @@ sysctl_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) if (func_proto) return func_proto; + func_proto = cgroup_current_func_proto(func_id, prog); + if (func_proto) + return func_proto; + switch (func_id) { case BPF_FUNC_sysctl_get_name: return &bpf_sysctl_get_name_proto; @@ -2343,6 +2351,10 @@ cg_sockopt_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) if (func_proto) return func_proto; + func_proto = cgroup_current_func_proto(func_id, prog); + if (func_proto) + return func_proto; + switch (func_id) { #ifdef CONFIG_NET case BPF_FUNC_get_netns_cookie: @@ -2589,3 +2601,16 @@ cgroup_common_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return NULL; } } + +const struct bpf_func_proto * +cgroup_current_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) +{ + switch (func_id) { +#ifdef CONFIG_CGROUP_NET_CLASSID + case BPF_FUNC_get_cgroup_classid: + return &bpf_get_cgroup_classid_curr_proto; +#endif + default: + return NULL; + } +} diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index b71e428ad936..9d0d54f4f0de 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2024,10 +2024,6 @@ bpf_base_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_get_current_ancestor_cgroup_id_proto; case BPF_FUNC_current_task_under_cgroup: return &bpf_current_task_under_cgroup_proto; -#endif -#ifdef CONFIG_CGROUP_NET_CLASSID - case BPF_FUNC_get_cgroup_classid: - return &bpf_get_cgroup_classid_curr_proto; #endif case BPF_FUNC_task_storage_get: if (bpf_prog_check_recur(prog)) -- 2.47.1
