[PATCH v11 bpf-next 5/7] bpf: Use btf_kfunc_id_set.remap logic for bpf_dynptr_from_skb
From: Song Liu <song@kernel.org>
Date: 2025-01-29 21:00:42
Also in:
bpf, linux-fsdevel, lkml
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), bpf [networking] (tcx & tc bpf, sock_addr), networking [general], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Martin KaFai Lau, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
btf_kfunc_id_set.remap can pick proper version of a kfunc for the calling context. Use this logic to select bpf_dynptr_from_skb or bpf_dynptr_from_skb_rdonly. This will make the verifier simpler. Unfortunately, btf_kfunc_id_set.remap cannot cover the DYNPTR_TYPE_SKB logic in check_kfunc_args(). This can be addressed later. Signed-off-by: Song Liu <song@kernel.org> --- kernel/bpf/verifier.c | 25 ++++++---------------- net/core/filter.c | 49 +++++++++++++++++++++++++++++++++++++++---- 2 files changed, 51 insertions(+), 23 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2188b6674266..55e710e318e5 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c@@ -11750,6 +11750,7 @@ enum special_kfunc_type { KF_bpf_rbtree_add_impl, KF_bpf_rbtree_first, KF_bpf_dynptr_from_skb, + KF_bpf_dynptr_from_skb_rdonly, KF_bpf_dynptr_from_xdp, KF_bpf_dynptr_slice, KF_bpf_dynptr_slice_rdwr,
@@ -11785,6 +11786,7 @@ BTF_ID(func, bpf_rbtree_add_impl) BTF_ID(func, bpf_rbtree_first) #ifdef CONFIG_NET BTF_ID(func, bpf_dynptr_from_skb) +BTF_ID(func, bpf_dynptr_from_skb_rdonly) BTF_ID(func, bpf_dynptr_from_xdp) #endif BTF_ID(func, bpf_dynptr_slice)
@@ -11816,10 +11818,12 @@ BTF_ID(func, bpf_rbtree_add_impl) BTF_ID(func, bpf_rbtree_first) #ifdef CONFIG_NET BTF_ID(func, bpf_dynptr_from_skb) +BTF_ID(func, bpf_dynptr_from_skb_rdonly) BTF_ID(func, bpf_dynptr_from_xdp) #else BTF_ID_UNUSED BTF_ID_UNUSED +BTF_ID_UNUSED #endif BTF_ID(func, bpf_dynptr_slice) BTF_ID(func, bpf_dynptr_slice_rdwr)
@@ -12741,7 +12745,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ if (is_kfunc_arg_uninit(btf, &args[i])) dynptr_arg_type |= MEM_UNINIT; - if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_skb]) { + if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_skb] || + meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_skb_rdonly]) { dynptr_arg_type |= DYNPTR_TYPE_SKB; } else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_xdp]) { dynptr_arg_type |= DYNPTR_TYPE_XDP;
@@ -20898,9 +20903,7 @@ static void specialize_kfunc(struct bpf_verifier_env *env, u32 func_id, u16 offset, unsigned long *addr) { struct bpf_prog *prog = env->prog; - bool seen_direct_write; void *xdp_kfunc; - bool is_rdonly; if (bpf_dev_bound_kfunc_id(func_id)) { xdp_kfunc = bpf_dev_bound_resolve_kfunc(prog, func_id);
@@ -20910,22 +20913,6 @@ static void specialize_kfunc(struct bpf_verifier_env *env, } /* fallback to default kfunc when not supported by netdev */ } - - if (offset) - return; - - if (func_id == special_kfunc_list[KF_bpf_dynptr_from_skb]) { - seen_direct_write = env->seen_direct_write; - is_rdonly = !may_access_direct_pkt_data(env, NULL, BPF_WRITE); - - if (is_rdonly) - *addr = (unsigned long)bpf_dynptr_from_skb_rdonly; - - /* restore env->seen_direct_write to its original value, since - * may_access_direct_pkt_data mutates it - */ - env->seen_direct_write = seen_direct_write; - } } static void __fixup_collection_insert_kfunc(struct bpf_insn_aux_data *insn_aux,
diff --git a/net/core/filter.c b/net/core/filter.c
index 2ec162dd83c4..6416689e3976 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c@@ -12062,10 +12062,8 @@ __bpf_kfunc int bpf_sk_assign_tcp_reqsk(struct __sk_buff *s, struct sock *sk, #endif } -__bpf_kfunc_end_defs(); - -int bpf_dynptr_from_skb_rdonly(struct __sk_buff *skb, u64 flags, - struct bpf_dynptr *ptr__uninit) +__bpf_kfunc int bpf_dynptr_from_skb_rdonly(struct __sk_buff *skb, u64 flags, + struct bpf_dynptr *ptr__uninit) { struct bpf_dynptr_kern *ptr = (struct bpf_dynptr_kern *)ptr__uninit; int err;
@@ -12079,10 +12077,16 @@ int bpf_dynptr_from_skb_rdonly(struct __sk_buff *skb, u64 flags, return 0; } +__bpf_kfunc_end_defs(); + BTF_KFUNCS_START(bpf_kfunc_check_set_skb) BTF_ID_FLAGS(func, bpf_dynptr_from_skb, KF_TRUSTED_ARGS) BTF_KFUNCS_END(bpf_kfunc_check_set_skb) +BTF_HIDDEN_KFUNCS_START(bpf_kfunc_check_hidden_set_skb) +BTF_ID_FLAGS(func, bpf_dynptr_from_skb_rdonly, KF_TRUSTED_ARGS) +BTF_KFUNCS_END(bpf_kfunc_check_hidden_set_skb) + BTF_KFUNCS_START(bpf_kfunc_check_set_xdp) BTF_ID_FLAGS(func, bpf_dynptr_from_xdp) BTF_KFUNCS_END(bpf_kfunc_check_set_xdp)
@@ -12095,9 +12099,46 @@ BTF_KFUNCS_START(bpf_kfunc_check_set_tcp_reqsk) BTF_ID_FLAGS(func, bpf_sk_assign_tcp_reqsk, KF_TRUSTED_ARGS) BTF_KFUNCS_END(bpf_kfunc_check_set_tcp_reqsk) +BTF_ID_LIST(bpf_dynptr_from_skb_list) +BTF_ID(func, bpf_dynptr_from_skb) +BTF_ID(func, bpf_dynptr_from_skb_rdonly) + +static u32 bpf_kfunc_set_skb_remap(const struct bpf_prog *prog, u32 kfunc_id) +{ + if (kfunc_id != bpf_dynptr_from_skb_list[0]) + return 0; + + switch (resolve_prog_type(prog)) { + /* Program types only with direct read access go here! */ + case BPF_PROG_TYPE_LWT_IN: + case BPF_PROG_TYPE_LWT_OUT: + case BPF_PROG_TYPE_LWT_SEG6LOCAL: + case BPF_PROG_TYPE_SK_REUSEPORT: + case BPF_PROG_TYPE_FLOW_DISSECTOR: + case BPF_PROG_TYPE_CGROUP_SKB: + return bpf_dynptr_from_skb_list[1]; + + /* Program types with direct read + write access go here! */ + case BPF_PROG_TYPE_SCHED_CLS: + case BPF_PROG_TYPE_SCHED_ACT: + case BPF_PROG_TYPE_XDP: + case BPF_PROG_TYPE_LWT_XMIT: + case BPF_PROG_TYPE_SK_SKB: + case BPF_PROG_TYPE_SK_MSG: + case BPF_PROG_TYPE_CGROUP_SOCKOPT: + return kfunc_id; + + default: + break; + } + return bpf_dynptr_from_skb_list[1]; +} + static const struct btf_kfunc_id_set bpf_kfunc_set_skb = { .owner = THIS_MODULE, .set = &bpf_kfunc_check_set_skb, + .hidden_set = &bpf_kfunc_check_hidden_set_skb, + .remap = &bpf_kfunc_set_skb_remap, }; static const struct btf_kfunc_id_set bpf_kfunc_set_xdp = {
--
2.43.5