6.8-stable review patch. If anyone has any objections, please let me know.
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From: Alexei Starovoitov ast@kernel.org
[ Upstream commit 0db63c0b86e981a1e97d2596d64ceceba1a5470e ]
The verifier assumes that 'sk' field in 'struct socket' is valid and non-NULL when 'socket' pointer itself is trusted and non-NULL. That may not be the case when socket was just created and passed to LSM socket_accept hook. Fix this verifier assumption and adjust tests.
Reported-by: Liam Wisehart liamwisehart@meta.com Acked-by: Kumar Kartikeya Dwivedi memxor@gmail.com Fixes: 6fcd486b3a0a ("bpf: Refactor RCU enforcement in the verifier.") Signed-off-by: Alexei Starovoitov ast@kernel.org Link: https://lore.kernel.org/r/20240427002544.68803-1-alexei.starovoitov@gmail.co... Signed-off-by: Martin KaFai Lau martin.lau@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/verifier.c | 23 +++++++++++++++---- .../bpf/progs/bench_local_storage_create.c | 5 ++-- .../selftests/bpf/progs/local_storage.c | 20 ++++++++-------- .../testing/selftests/bpf/progs/lsm_cgroup.c | 8 +++++-- 4 files changed, 38 insertions(+), 18 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 68ec508057466..6edfcc3375082 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2328,6 +2328,8 @@ static void mark_btf_ld_reg(struct bpf_verifier_env *env, regs[regno].type = PTR_TO_BTF_ID | flag; regs[regno].btf = btf; regs[regno].btf_id = btf_id; + if (type_may_be_null(flag)) + regs[regno].id = ++env->id_gen; }
#define DEF_NOT_SUBREG (0) @@ -5322,8 +5324,6 @@ static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno, */ mark_btf_ld_reg(env, cur_regs(env), value_regno, PTR_TO_BTF_ID, kptr_field->kptr.btf, kptr_field->kptr.btf_id, btf_ld_kptr_type(env, kptr_field)); - /* For mark_ptr_or_null_reg */ - val_reg->id = ++env->id_gen; } else if (class == BPF_STX) { val_reg = reg_state(env, value_regno); if (!register_is_null(val_reg) && @@ -5634,7 +5634,8 @@ static bool is_trusted_reg(const struct bpf_reg_state *reg) return true;
/* Types listed in the reg2btf_ids are always trusted */ - if (reg2btf_ids[base_type(reg->type)]) + if (reg2btf_ids[base_type(reg->type)] && + !bpf_type_has_unsafe_modifiers(reg->type)) return true;
/* If a register is not referenced, it is trusted if it has the @@ -6244,6 +6245,7 @@ static int bpf_map_direct_read(struct bpf_map *map, int off, int size, u64 *val, #define BTF_TYPE_SAFE_RCU(__type) __PASTE(__type, __safe_rcu) #define BTF_TYPE_SAFE_RCU_OR_NULL(__type) __PASTE(__type, __safe_rcu_or_null) #define BTF_TYPE_SAFE_TRUSTED(__type) __PASTE(__type, __safe_trusted) +#define BTF_TYPE_SAFE_TRUSTED_OR_NULL(__type) __PASTE(__type, __safe_trusted_or_null)
/* * Allow list few fields as RCU trusted or full trusted. @@ -6307,7 +6309,7 @@ BTF_TYPE_SAFE_TRUSTED(struct dentry) { struct inode *d_inode; };
-BTF_TYPE_SAFE_TRUSTED(struct socket) { +BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket) { struct sock *sk; };
@@ -6342,11 +6344,20 @@ static bool type_is_trusted(struct bpf_verifier_env *env, BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED(struct linux_binprm)); BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED(struct file)); BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED(struct dentry)); - BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED(struct socket));
return btf_nested_type_is_trusted(&env->log, reg, field_name, btf_id, "__safe_trusted"); }
+static bool type_is_trusted_or_null(struct bpf_verifier_env *env, + struct bpf_reg_state *reg, + const char *field_name, u32 btf_id) +{ + BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket)); + + return btf_nested_type_is_trusted(&env->log, reg, field_name, btf_id, + "__safe_trusted_or_null"); +} + static int check_ptr_to_btf_access(struct bpf_verifier_env *env, struct bpf_reg_state *regs, int regno, int off, int size, @@ -6455,6 +6466,8 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env, */ if (type_is_trusted(env, reg, field_name, btf_id)) { flag |= PTR_TRUSTED; + } else if (type_is_trusted_or_null(env, reg, field_name, btf_id)) { + flag |= PTR_TRUSTED | PTR_MAYBE_NULL; } else if (in_rcu_cs(env) && !type_may_be_null(reg->type)) { if (type_is_rcu(env, reg, field_name, btf_id)) { /* ignore __rcu tag and mark it MEM_RCU */ diff --git a/tools/testing/selftests/bpf/progs/bench_local_storage_create.c b/tools/testing/selftests/bpf/progs/bench_local_storage_create.c index e4bfbba6c1936..c8ec0d0368e4a 100644 --- a/tools/testing/selftests/bpf/progs/bench_local_storage_create.c +++ b/tools/testing/selftests/bpf/progs/bench_local_storage_create.c @@ -61,14 +61,15 @@ SEC("lsm.s/socket_post_create") int BPF_PROG(socket_post_create, struct socket *sock, int family, int type, int protocol, int kern) { + struct sock *sk = sock->sk; struct storage *stg; __u32 pid;
pid = bpf_get_current_pid_tgid() >> 32; - if (pid != bench_pid) + if (pid != bench_pid || !sk) return 0;
- stg = bpf_sk_storage_get(&sk_storage_map, sock->sk, NULL, + stg = bpf_sk_storage_get(&sk_storage_map, sk, NULL, BPF_LOCAL_STORAGE_GET_F_CREATE);
if (stg) diff --git a/tools/testing/selftests/bpf/progs/local_storage.c b/tools/testing/selftests/bpf/progs/local_storage.c index e5e3a8b8dd075..637e75df2e146 100644 --- a/tools/testing/selftests/bpf/progs/local_storage.c +++ b/tools/testing/selftests/bpf/progs/local_storage.c @@ -140,11 +140,12 @@ int BPF_PROG(socket_bind, struct socket *sock, struct sockaddr *address, { __u32 pid = bpf_get_current_pid_tgid() >> 32; struct local_storage *storage; + struct sock *sk = sock->sk;
- if (pid != monitored_pid) + if (pid != monitored_pid || !sk) return 0;
- storage = bpf_sk_storage_get(&sk_storage_map, sock->sk, 0, 0); + storage = bpf_sk_storage_get(&sk_storage_map, sk, 0, 0); if (!storage) return 0;
@@ -155,24 +156,24 @@ int BPF_PROG(socket_bind, struct socket *sock, struct sockaddr *address, /* This tests that we can associate multiple elements * with the local storage. */ - storage = bpf_sk_storage_get(&sk_storage_map2, sock->sk, 0, + storage = bpf_sk_storage_get(&sk_storage_map2, sk, 0, BPF_LOCAL_STORAGE_GET_F_CREATE); if (!storage) return 0;
- if (bpf_sk_storage_delete(&sk_storage_map2, sock->sk)) + if (bpf_sk_storage_delete(&sk_storage_map2, sk)) return 0;
- storage = bpf_sk_storage_get(&sk_storage_map2, sock->sk, 0, + storage = bpf_sk_storage_get(&sk_storage_map2, sk, 0, BPF_LOCAL_STORAGE_GET_F_CREATE); if (!storage) return 0;
- if (bpf_sk_storage_delete(&sk_storage_map, sock->sk)) + if (bpf_sk_storage_delete(&sk_storage_map, sk)) return 0;
/* Ensure that the sk_storage_map is disconnected from the storage. */ - if (!sock->sk->sk_bpf_storage || sock->sk->sk_bpf_storage->smap) + if (!sk->sk_bpf_storage || sk->sk_bpf_storage->smap) return 0;
sk_storage_result = 0; @@ -185,11 +186,12 @@ int BPF_PROG(socket_post_create, struct socket *sock, int family, int type, { __u32 pid = bpf_get_current_pid_tgid() >> 32; struct local_storage *storage; + struct sock *sk = sock->sk;
- if (pid != monitored_pid) + if (pid != monitored_pid || !sk) return 0;
- storage = bpf_sk_storage_get(&sk_storage_map, sock->sk, 0, + storage = bpf_sk_storage_get(&sk_storage_map, sk, 0, BPF_LOCAL_STORAGE_GET_F_CREATE); if (!storage) return 0; diff --git a/tools/testing/selftests/bpf/progs/lsm_cgroup.c b/tools/testing/selftests/bpf/progs/lsm_cgroup.c index 02c11d16b692a..d7598538aa2da 100644 --- a/tools/testing/selftests/bpf/progs/lsm_cgroup.c +++ b/tools/testing/selftests/bpf/progs/lsm_cgroup.c @@ -103,11 +103,15 @@ static __always_inline int real_bind(struct socket *sock, int addrlen) { struct sockaddr_ll sa = {}; + struct sock *sk = sock->sk;
- if (sock->sk->__sk_common.skc_family != AF_PACKET) + if (!sk) + return 1; + + if (sk->__sk_common.skc_family != AF_PACKET) return 1;
- if (sock->sk->sk_kern_sock) + if (sk->sk_kern_sock) return 1;
bpf_probe_read_kernel(&sa, sizeof(sa), address);