diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 4c54864316ee..5739cc9986f8 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -927,6 +927,7 @@ struct bpf_insn_access_aux { }; }; struct bpf_verifier_log *log; /* for verbose logs */ + bool is_retval; /* is accessing function return value ? */ }; static inline void diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h index 1de7ece5d36d..aefcd6564251 100644 --- a/include/linux/bpf_lsm.h +++ b/include/linux/bpf_lsm.h @@ -9,6 +9,7 @@ #include #include +#include #include #ifdef CONFIG_BPF_LSM @@ -45,6 +46,8 @@ void bpf_inode_storage_free(struct inode *inode); void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, bpf_func_t *bpf_func); +int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *range); #else /* !CONFIG_BPF_LSM */ static inline bool bpf_lsm_is_sleepable_hook(u32 btf_id) @@ -78,6 +81,11 @@ static inline void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, { } +static inline int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *range) +{ + return -EOPNOTSUPP; +} #endif /* CONFIG_BPF_LSM */ #endif /* _LINUX_BPF_LSM_H */ diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index 1f596ad6257c..6292ac5f9bd1 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -11,7 +11,6 @@ #include #include #include -#include #include #include #include @@ -417,3 +416,36 @@ const struct bpf_verifier_ops lsm_verifier_ops = { .get_func_proto = bpf_lsm_func_proto, .is_valid_access = btf_ctx_access, }; + +/* hooks return 0 or 1 */ +BTF_SET_START(bool_lsm_hooks) +#ifdef CONFIG_SECURITY_NETWORK_XFRM +BTF_ID(func, bpf_lsm_xfrm_state_pol_flow_match) +#endif +#ifdef CONFIG_AUDIT +BTF_ID(func, bpf_lsm_audit_rule_known) +#endif +BTF_ID(func, bpf_lsm_inode_xattr_skipcap) +BTF_SET_END(bool_lsm_hooks) + +int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *retval_range) +{ + /* no return value range for void hooks */ + if (!prog->aux->attach_func_proto->type) + return -EINVAL; + + if (btf_id_set_contains(&bool_lsm_hooks, prog->aux->attach_btf_id)) { + retval_range->minval = 0; + retval_range->maxval = 1; + } else { + /* All other available LSM hooks, except task_prctl, return 0 + * on success and negative error code on failure. + * To keep things simple, we only allow bpf progs to return 0 + * or negative errno for task_prctl too. + */ + retval_range->minval = -MAX_ERRNO; + retval_range->maxval = 0; + } + return 0; +} diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 520f49f422fe..95426d5b634e 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6416,8 +6416,11 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, if (arg == nr_args) { switch (prog->expected_attach_type) { - case BPF_LSM_CGROUP: case BPF_LSM_MAC: + /* mark we are accessing the return value */ + info->is_retval = true; + fallthrough; + case BPF_LSM_CGROUP: case BPF_TRACE_FEXIT: /* When LSM programs are attached to void LSM hooks * they use FEXIT trampolines and when attached to diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 247a038d3a14..8caa7322f031 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2334,6 +2334,25 @@ static void mark_reg_unknown(struct bpf_verifier_env *env, __mark_reg_unknown(env, regs + regno); } +static int __mark_reg_s32_range(struct bpf_verifier_env *env, + struct bpf_reg_state *regs, + u32 regno, + s32 s32_min, + s32 s32_max) +{ + struct bpf_reg_state *reg = regs + regno; + + reg->s32_min_value = max_t(s32, reg->s32_min_value, s32_min); + reg->s32_max_value = min_t(s32, reg->s32_max_value, s32_max); + + reg->smin_value = max_t(s64, reg->smin_value, s32_min); + reg->smax_value = min_t(s64, reg->smax_value, s32_max); + + reg_bounds_sync(reg); + + return reg_bounds_sanity_check(env, reg, "s32_range"); +} + static void __mark_reg_not_init(const struct bpf_verifier_env *env, struct bpf_reg_state *reg) { @@ -5607,11 +5626,12 @@ static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off, /* check access to 'struct bpf_context' fields. Supports fixed offsets only */ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size, enum bpf_access_type t, enum bpf_reg_type *reg_type, - struct btf **btf, u32 *btf_id) + struct btf **btf, u32 *btf_id, bool *is_retval) { struct bpf_insn_access_aux info = { .reg_type = *reg_type, .log = &env->log, + .is_retval = false, }; if (env->ops->is_valid_access && @@ -5624,6 +5644,7 @@ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, * type of narrower access. */ *reg_type = info.reg_type; + *is_retval = info.is_retval; if (base_type(*reg_type) == PTR_TO_BTF_ID) { *btf = info.btf; @@ -6792,6 +6813,17 @@ static int check_stack_access_within_bounds( return grow_stack_state(env, state, -min_off /* size */); } +static bool get_func_retval_range(struct bpf_prog *prog, + struct bpf_retval_range *range) +{ + if (prog->type == BPF_PROG_TYPE_LSM && + prog->expected_attach_type == BPF_LSM_MAC && + !bpf_lsm_get_retval_range(prog, range)) { + return true; + } + return false; +} + /* check whether memory at (regno + off) is accessible for t = (read | write) * if t==write, value_regno is a register which value is stored into memory * if t==read, value_regno is a register which will receive the value from memory @@ -6896,6 +6928,8 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn if (!err && value_regno >= 0 && (t == BPF_READ || rdonly_mem)) mark_reg_unknown(env, regs, value_regno); } else if (reg->type == PTR_TO_CTX) { + bool is_retval = false; + struct bpf_retval_range range; enum bpf_reg_type reg_type = SCALAR_VALUE; struct btf *btf = NULL; u32 btf_id = 0; @@ -6911,7 +6945,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn return err; err = check_ctx_access(env, insn_idx, off, size, t, ®_type, &btf, - &btf_id); + &btf_id, &is_retval); if (err) verbose_linfo(env, insn_idx, "; "); if (!err && t == BPF_READ && value_regno >= 0) { @@ -6920,7 +6954,14 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn * case, we know the offset is zero. */ if (reg_type == SCALAR_VALUE) { - mark_reg_unknown(env, regs, value_regno); + if (is_retval && get_func_retval_range(env->prog, &range)) { + err = __mark_reg_s32_range(env, regs, value_regno, + range.minval, range.maxval); + if (err) + return err; + } else { + mark_reg_unknown(env, regs, value_regno); + } } else { mark_reg_known_zero(env, regs, value_regno); @@ -15762,12 +15803,13 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char case BPF_PROG_TYPE_LSM: if (env->prog->expected_attach_type != BPF_LSM_CGROUP) { - /* Regular BPF_PROG_TYPE_LSM programs can return - * any value. - */ - return 0; - } - if (!env->prog->aux->attach_func_proto->type) { + /* no range found, any return value is allowed */ + if (!get_func_retval_range(env->prog, &range)) + return 0; + /* no restricted range, any return value is allowed */ + if (range.minval == S32_MIN && range.maxval == S32_MAX) + return 0; + } else if (!env->prog->aux->attach_func_proto->type) { /* Make sure programs that attach to void * hooks don't try to modify return value. */