From feb4adfad575c1e27cbfaa3462f376c13da36942 Mon Sep 17 00:00:00 2001 From: Dmitrii Banshchikov Date: Sat, 13 Feb 2021 00:56:39 +0400 Subject: bpf: Rename bpf_reg_state variables Using "reg" for an array of bpf_reg_state and "reg[i + 1]" for an individual bpf_reg_state is error-prone and verbose. Use "regs" for the former and "reg" for the latter as other code nearby does. Signed-off-by: Dmitrii Banshchikov Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20210212205642.620788-2-me@ubique.spb.ru --- kernel/bpf/btf.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 756a93f534b6..bd5d2c563693 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5291,7 +5291,7 @@ int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *pr * Only PTR_TO_CTX and SCALAR_VALUE states are recognized. */ int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, - struct bpf_reg_state *reg) + struct bpf_reg_state *regs) { struct bpf_verifier_log *log = &env->log; struct bpf_prog *prog = env->prog; @@ -5337,17 +5337,19 @@ int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, * verifier sees. */ for (i = 0; i < nargs; i++) { + struct bpf_reg_state *reg = ®s[i + 1]; + t = btf_type_by_id(btf, args[i].type); while (btf_type_is_modifier(t)) t = btf_type_by_id(btf, t->type); if (btf_type_is_int(t) || btf_type_is_enum(t)) { - if (reg[i + 1].type == SCALAR_VALUE) + if (reg->type == SCALAR_VALUE) continue; bpf_log(log, "R%d is not a scalar\n", i + 1); goto out; } if (btf_type_is_ptr(t)) { - if (reg[i + 1].type == SCALAR_VALUE) { + if (reg->type == SCALAR_VALUE) { bpf_log(log, "R%d is not a pointer\n", i + 1); goto out; } @@ -5355,13 +5357,13 @@ int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, * is passing PTR_TO_CTX. */ if (btf_get_prog_ctx_type(log, btf, t, prog->type, i)) { - if (reg[i + 1].type != PTR_TO_CTX) { + if (reg->type != PTR_TO_CTX) { bpf_log(log, "arg#%d expected pointer to ctx, but got %s\n", i, btf_kind_str[BTF_INFO_KIND(t->info)]); goto out; } - if (check_ctx_reg(env, ®[i + 1], i + 1)) + if (check_ctx_reg(env, reg, i + 1)) goto out; continue; } @@ -5388,7 +5390,7 @@ out: * (either PTR_TO_CTX or SCALAR_VALUE). */ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog, - struct bpf_reg_state *reg) + struct bpf_reg_state *regs) { struct bpf_verifier_log *log = &env->log; struct bpf_prog *prog = env->prog; @@ -5459,16 +5461,18 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog, * Only PTR_TO_CTX and SCALAR are supported atm. */ for (i = 0; i < nargs; i++) { + struct bpf_reg_state *reg = ®s[i + 1]; + t = btf_type_by_id(btf, args[i].type); while (btf_type_is_modifier(t)) t = btf_type_by_id(btf, t->type); if (btf_type_is_int(t) || btf_type_is_enum(t)) { - reg[i + 1].type = SCALAR_VALUE; + reg->type = SCALAR_VALUE; continue; } if (btf_type_is_ptr(t) && btf_get_prog_ctx_type(log, btf, t, prog_type, i)) { - reg[i + 1].type = PTR_TO_CTX; + reg->type = PTR_TO_CTX; continue; } bpf_log(log, "Arg#%d type %s in %s() is not supported yet.\n", -- cgit v1.2.3 From 4ddb74165ae580b6dcbb5ab1919d994fc8d03c3f Mon Sep 17 00:00:00 2001 From: Dmitrii Banshchikov Date: Sat, 13 Feb 2021 00:56:40 +0400 Subject: bpf: Extract nullable reg type conversion into a helper function Extract conversion from a register's nullable type to a type with a value. The helper will be used in mark_ptr_not_null_reg(). Signed-off-by: Dmitrii Banshchikov Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20210212205642.620788-3-me@ubique.spb.ru --- kernel/bpf/verifier.c | 83 ++++++++++++++++++++++++++++++++------------------- 1 file changed, 52 insertions(+), 31 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index beae700bb56e..a9f75bd7f8d3 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1079,6 +1079,51 @@ static void mark_reg_known_zero(struct bpf_verifier_env *env, __mark_reg_known_zero(regs + regno); } +static void mark_ptr_not_null_reg(struct bpf_reg_state *reg) +{ + switch (reg->type) { + case PTR_TO_MAP_VALUE_OR_NULL: { + const struct bpf_map *map = reg->map_ptr; + + if (map->inner_map_meta) { + reg->type = CONST_PTR_TO_MAP; + reg->map_ptr = map->inner_map_meta; + } else if (map->map_type == BPF_MAP_TYPE_XSKMAP) { + reg->type = PTR_TO_XDP_SOCK; + } else if (map->map_type == BPF_MAP_TYPE_SOCKMAP || + map->map_type == BPF_MAP_TYPE_SOCKHASH) { + reg->type = PTR_TO_SOCKET; + } else { + reg->type = PTR_TO_MAP_VALUE; + } + break; + } + case PTR_TO_SOCKET_OR_NULL: + reg->type = PTR_TO_SOCKET; + break; + case PTR_TO_SOCK_COMMON_OR_NULL: + reg->type = PTR_TO_SOCK_COMMON; + break; + case PTR_TO_TCP_SOCK_OR_NULL: + reg->type = PTR_TO_TCP_SOCK; + break; + case PTR_TO_BTF_ID_OR_NULL: + reg->type = PTR_TO_BTF_ID; + break; + case PTR_TO_MEM_OR_NULL: + reg->type = PTR_TO_MEM; + break; + case PTR_TO_RDONLY_BUF_OR_NULL: + reg->type = PTR_TO_RDONLY_BUF; + break; + case PTR_TO_RDWR_BUF_OR_NULL: + reg->type = PTR_TO_RDWR_BUF; + break; + default: + WARN_ON("unknown nullable register type"); + } +} + static bool reg_is_pkt_pointer(const struct bpf_reg_state *reg) { return type_is_pkt_pointer(reg->type); @@ -7737,43 +7782,19 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state, } if (is_null) { reg->type = SCALAR_VALUE; - } else if (reg->type == PTR_TO_MAP_VALUE_OR_NULL) { - const struct bpf_map *map = reg->map_ptr; - - if (map->inner_map_meta) { - reg->type = CONST_PTR_TO_MAP; - reg->map_ptr = map->inner_map_meta; - } else if (map->map_type == BPF_MAP_TYPE_XSKMAP) { - reg->type = PTR_TO_XDP_SOCK; - } else if (map->map_type == BPF_MAP_TYPE_SOCKMAP || - map->map_type == BPF_MAP_TYPE_SOCKHASH) { - reg->type = PTR_TO_SOCKET; - } else { - reg->type = PTR_TO_MAP_VALUE; - } - } else if (reg->type == PTR_TO_SOCKET_OR_NULL) { - reg->type = PTR_TO_SOCKET; - } else if (reg->type == PTR_TO_SOCK_COMMON_OR_NULL) { - reg->type = PTR_TO_SOCK_COMMON; - } else if (reg->type == PTR_TO_TCP_SOCK_OR_NULL) { - reg->type = PTR_TO_TCP_SOCK; - } else if (reg->type == PTR_TO_BTF_ID_OR_NULL) { - reg->type = PTR_TO_BTF_ID; - } else if (reg->type == PTR_TO_MEM_OR_NULL) { - reg->type = PTR_TO_MEM; - } else if (reg->type == PTR_TO_RDONLY_BUF_OR_NULL) { - reg->type = PTR_TO_RDONLY_BUF; - } else if (reg->type == PTR_TO_RDWR_BUF_OR_NULL) { - reg->type = PTR_TO_RDWR_BUF; - } - if (is_null) { /* We don't need id and ref_obj_id from this point * onwards anymore, thus we should better reset it, * so that state pruning has chances to take effect. */ reg->id = 0; reg->ref_obj_id = 0; - } else if (!reg_may_point_to_spin_lock(reg)) { + + return; + } + + mark_ptr_not_null_reg(reg); + + if (!reg_may_point_to_spin_lock(reg)) { /* For not-NULL ptr, reg->ref_obj_id will be reset * in release_reg_references(). * -- cgit v1.2.3 From e5069b9c23b3857db986c58801bebe450cff3392 Mon Sep 17 00:00:00 2001 From: Dmitrii Banshchikov Date: Sat, 13 Feb 2021 00:56:41 +0400 Subject: bpf: Support pointers in global func args Add an ability to pass a pointer to a type with known size in arguments of a global function. Such pointers may be used to overcome the limit on the maximum number of arguments, avoid expensive and tricky workarounds and to have multiple output arguments. A referenced type may contain pointers but indirect access through them isn't supported. The implementation consists of two parts. If a global function has an argument that is a pointer to a type with known size then: 1) In btf_check_func_arg_match(): check that the corresponding register points to NULL or to a valid memory region that is large enough to contain the expected argument's type. 2) In btf_prepare_func_args(): set the corresponding register type to PTR_TO_MEM_OR_NULL and its size to the size of the expected type. Only global functions are supported because allowance of pointers for static functions might break validation. Consider the following scenario. A static function has a pointer argument. A caller passes pointer to its stack memory. Because the callee can change referenced memory verifier cannot longer assume any particular slot type of the caller's stack memory hence the slot type is changed to SLOT_MISC. If there is an operation that relies on slot type other than SLOT_MISC then verifier won't be able to infer safety of the operation. When verifier sees a static function that has a pointer argument different from PTR_TO_CTX then it skips arguments check and continues with "inline" validation with more information available. The operation that relies on the particular slot type now succeeds. Because global functions were not allowed to have pointer arguments different from PTR_TO_CTX it's not possible to break existing and valid code. Signed-off-by: Dmitrii Banshchikov Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20210212205642.620788-4-me@ubique.spb.ru --- kernel/bpf/btf.c | 55 +++++++++++++++++++++++++++++++++++++++++---------- kernel/bpf/verifier.c | 30 ++++++++++++++++++++++++++++ 2 files changed, 75 insertions(+), 10 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index bd5d2c563693..2efeb5f4b343 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5297,9 +5297,10 @@ int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, struct bpf_prog *prog = env->prog; struct btf *btf = prog->aux->btf; const struct btf_param *args; - const struct btf_type *t; - u32 i, nargs, btf_id; + const struct btf_type *t, *ref_t; + u32 i, nargs, btf_id, type_size; const char *tname; + bool is_global; if (!prog->aux->func_info) return -EINVAL; @@ -5333,6 +5334,8 @@ int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, bpf_log(log, "Function %s has %d > 5 args\n", tname, nargs); goto out; } + + is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL; /* check that BTF function arguments match actual types that the * verifier sees. */ @@ -5349,10 +5352,6 @@ int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, goto out; } if (btf_type_is_ptr(t)) { - if (reg->type == SCALAR_VALUE) { - bpf_log(log, "R%d is not a pointer\n", i + 1); - goto out; - } /* If function expects ctx type in BTF check that caller * is passing PTR_TO_CTX. */ @@ -5367,6 +5366,25 @@ int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, goto out; continue; } + + if (!is_global) + goto out; + + t = btf_type_skip_modifiers(btf, t->type, NULL); + + ref_t = btf_resolve_size(btf, t, &type_size); + if (IS_ERR(ref_t)) { + bpf_log(log, + "arg#%d reference type('%s %s') size cannot be determined: %ld\n", + i, btf_type_str(t), btf_name_by_offset(btf, t->name_off), + PTR_ERR(ref_t)); + goto out; + } + + if (check_mem_reg(env, reg, i + 1, type_size)) + goto out; + + continue; } bpf_log(log, "Unrecognized arg#%d type %s\n", i, btf_kind_str[BTF_INFO_KIND(t->info)]); @@ -5397,7 +5415,7 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog, enum bpf_prog_type prog_type = prog->type; struct btf *btf = prog->aux->btf; const struct btf_param *args; - const struct btf_type *t; + const struct btf_type *t, *ref_t; u32 i, nargs, btf_id; const char *tname; @@ -5470,9 +5488,26 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog, reg->type = SCALAR_VALUE; continue; } - if (btf_type_is_ptr(t) && - btf_get_prog_ctx_type(log, btf, t, prog_type, i)) { - reg->type = PTR_TO_CTX; + if (btf_type_is_ptr(t)) { + if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) { + reg->type = PTR_TO_CTX; + continue; + } + + t = btf_type_skip_modifiers(btf, t->type, NULL); + + ref_t = btf_resolve_size(btf, t, ®->mem_size); + if (IS_ERR(ref_t)) { + bpf_log(log, + "arg#%d reference type('%s %s') size cannot be determined: %ld\n", + i, btf_type_str(t), btf_name_by_offset(btf, t->name_off), + PTR_ERR(ref_t)); + return -EINVAL; + } + + reg->type = PTR_TO_MEM_OR_NULL; + reg->id = ++env->id_gen; + continue; } bpf_log(log, "Arg#%d type %s in %s() is not supported yet.\n", diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a9f75bd7f8d3..11a242932a2c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4272,6 +4272,29 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno, } } +int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg, + u32 regno, u32 mem_size) +{ + if (register_is_null(reg)) + return 0; + + if (reg_type_may_be_null(reg->type)) { + /* Assuming that the register contains a value check if the memory + * access is safe. Temporarily save and restore the register's state as + * the conversion shouldn't be visible to a caller. + */ + const struct bpf_reg_state saved_reg = *reg; + int rv; + + mark_ptr_not_null_reg(reg); + rv = check_helper_mem_access(env, regno, mem_size, true, NULL); + *reg = saved_reg; + return rv; + } + + return check_helper_mem_access(env, regno, mem_size, true, NULL); +} + /* Implementation details: * bpf_map_lookup returns PTR_TO_MAP_VALUE_OR_NULL * Two bpf_map_lookups (even with the same key) will have different reg->id. @@ -11960,6 +11983,13 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog) mark_reg_known_zero(env, regs, i); else if (regs[i].type == SCALAR_VALUE) mark_reg_unknown(env, regs, i); + else if (regs[i].type == PTR_TO_MEM_OR_NULL) { + const u32 mem_size = regs[i].mem_size; + + mark_reg_known_zero(env, regs, i); + regs[i].mem_size = mem_size; + regs[i].id = ++env->id_gen; + } } } else { /* 1st arg to a function */ -- cgit v1.2.3