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Thu, 27 Mar 2025 16:22:53 +0800 (CST) From: Hou Tao To: bpf@vger.kernel.org Cc: Martin KaFai Lau , Alexei Starovoitov , Andrii Nakryiko , Eduard Zingerman , Song Liu , Hao Luo , Yonghong Song , Daniel Borkmann , KP Singh , Stanislav Fomichev , Jiri Olsa , John Fastabend , houtao1@huawei.com Subject: [PATCH bpf-next v3 05/16] bpf: Support map key with dynptr in verifier Date: Thu, 27 Mar 2025 16:34:44 +0800 Message-Id: <20250327083455.848708-6-houtao@huaweicloud.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20250327083455.848708-1-houtao@huaweicloud.com> References: <20250327083455.848708-1-houtao@huaweicloud.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: gCh0CgAXe1_XCuVnluzSHg--.7420S9 X-Coremail-Antispam: 1UD129KBjvJXoW3ArWxXw48Aw43Gw4DKry5XFb_yoW3ur4UpF 4kG3sxWr4kKr4IvwsFqFsrAF15Kw1Iqw47GrWrK340yFyrXrZ09Fy0kFyUur13trZ8C347 Jw1qqFZ8uw4UJFJanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPSb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUAV Cq3wA2048vs2IY020Ec7CjxVAFwI0_Xr0E3s1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0 rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267 AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E 14v26rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7 xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Y z7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1lc7CjxVAaw2 AFwI0_Jw0_GFyl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAq x4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r 43MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_JFI_Gr1lIxAIcVC0I7IYx2IY6xkF 7I0E14v26F4j6r4UJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI 0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7I U1aLvJUUUUU== X-CM-SenderInfo: xkrx3t3r6k3tpzhluzxrxghudrp/ X-Patchwork-Delegate: bpf@iogearbox.net From: Hou Tao The patch basically does the following three things to enable dynptr key for bpf map: 1) Only allow PTR_TO_STACK typed register for dynptr key The main reason is that bpf_dynptr can only be defined in the stack, so for dynptr key only PTR_TO_STACK typed register is allowed. bpf_dynptr could also be represented by CONST_PTR_TO_DYNPTR typed register (e.g., in callback func or subprog), but it is not supported now. 2) Only allow fixed-offset for PTR_TO_STACK register Variable-offset for PTR_TO_STACK typed register is disallowed, because it is impossible to check whether or not the stack access is aligned with BPF_REG_SIZE and is matched with the location of dynptr or non-dynptr part in the map key. 3) Check the layout of the stack content is matched with the btf_record Firstly check the start offset of the stack access is aligned with BPF_REG_SIZE, then check the offset and the size of dynptr/non-dynptr parts in the stack range is consistent with the btf_record of the map key. Signed-off-by: Hou Tao --- kernel/bpf/verifier.c | 186 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 173 insertions(+), 13 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 9d611d5152789..05a5636ae4984 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7950,9 +7950,90 @@ static int allow_uninitialized_stack_range(struct bpf_verifier_env *env, int reg return 1; } +struct dynptr_key_state { + const struct btf_record *rec; + const struct btf_field *cur_dynptr; + bool valid_dynptr_id; + int cur_dynptr_id; +}; + +static int init_dynptr_key_state(struct bpf_verifier_env *env, const struct btf_record *rec, + struct dynptr_key_state *state) +{ + unsigned int i; + + /* Find the first dynptr in the dynptr-key */ + for (i = 0; i < rec->cnt; i++) { + if (rec->fields[i].type == BPF_DYNPTR) + break; + } + if (i >= rec->cnt) { + verbose(env, "verifier bug: dynptr not found\n"); + return -EFAULT; + } + + state->rec = rec; + state->cur_dynptr = &rec->fields[i]; + state->valid_dynptr_id = false; + + return 0; +} + +static int check_dynptr_key_access(struct bpf_verifier_env *env, struct dynptr_key_state *state, + struct bpf_reg_state *reg, u8 stype, int offset) +{ + const struct btf_field *dynptr = state->cur_dynptr; + + /* Non-dynptr part before a dynptr or non-dynptr part after + * the last dynptr. + */ + if (offset < dynptr->offset || offset >= dynptr->offset + dynptr->size) { + if (stype == STACK_DYNPTR) { + verbose(env, + "dynptr-key expects non-dynptr at offset %d cur_dynptr_offset %u\n", + offset, dynptr->offset); + return -EACCES; + } + } else { + if (stype != STACK_DYNPTR) { + verbose(env, + "dynptr-key expects dynptr at offset %d cur_dynptr_offset %u\n", + offset, dynptr->offset); + return -EACCES; + } + + /* A dynptr is composed of parts from two dynptrs */ + if (state->valid_dynptr_id && reg->id != state->cur_dynptr_id) { + verbose(env, "malformed dynptr-key at offset %d cur_dynptr_offset %u\n", + offset, dynptr->offset); + return -EACCES; + } + if (!state->valid_dynptr_id) { + state->valid_dynptr_id = true; + state->cur_dynptr_id = reg->id; + } + + if (offset == dynptr->offset + dynptr->size - 1) { + const struct btf_record *rec = state->rec; + unsigned int i; + + for (i = dynptr - rec->fields + 1; i < rec->cnt; i++) { + if (rec->fields[i].type == BPF_DYNPTR) { + state->cur_dynptr = &rec->fields[i]; + state->valid_dynptr_id = false; + break; + } + } + } + } + + return 0; +} + static int check_stack_range_initialized(struct bpf_verifier_env *env, int regno, int min_off, int max_off, int access_size, - enum bpf_access_type type) + enum bpf_access_type type, + struct dynptr_key_state *dynkey) { struct bpf_reg_state *reg = reg_state(env, regno); struct bpf_func_state *state = func(env, reg); @@ -7975,6 +8056,8 @@ static int check_stack_range_initialized(struct bpf_verifier_env *env, int regno stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE]; if (*stype == STACK_MISC) goto mark; + if (dynkey && *stype == STACK_DYNPTR) + goto mark; if ((*stype == STACK_ZERO) || (*stype == STACK_INVALID && env->allow_uninit_stack)) { if (clobber) { @@ -8007,6 +8090,15 @@ static int check_stack_range_initialized(struct bpf_verifier_env *env, int regno } return -EACCES; mark: + if (dynkey) { + int err = check_dynptr_key_access(env, dynkey, + &state->stack[spi].spilled_ptr, + *stype, i - min_off); + + if (err) + return err; + } + /* reading any byte out of 8-byte 'spill_slot' will cause * the whole slot to be marked as 'read' * @@ -8058,7 +8150,60 @@ static int check_stack_range_access(struct bpf_verifier_env *env, int regno, int if (err > 0) return 0; - return check_stack_range_initialized(env, regno, min_off, max_off, access_size, type); + return check_stack_range_initialized(env, regno, min_off, max_off, access_size, type, NULL); +} + +static int check_dynkey_stack_access_offset(struct bpf_verifier_env *env, int regno, int off) +{ + struct bpf_reg_state *reg = reg_state(env, regno); + + if (!tnum_is_const(reg->var_off)) { + verbose(env, "R%d variable offset prohibited for dynptr-key\n", regno); + return -EACCES; + } + + off = reg->var_off.value + off; + if (off % BPF_REG_SIZE) { + verbose(env, "R%d misaligned offset %d for dynptr-key\n", regno, off); + return -EACCES; + } + + return 0; +} + +/* It is almost the same as check_stack_range_access(), except the following + * things: + * (1) no need to check whether access_size is zero (due to non-zero key_size) + * (2) disallow uninitialized stack range + * (3) need BPF_REG_SIZE-aligned access with fixed-size offset + * (4) need to check whether the layout of bpf_dynptr part and non-bpf_dynptr + * part in the stack range is the same as the layout of dynptr key + */ +static int check_dynkey_stack_range_access(struct bpf_verifier_env *env, int regno, int off, + int access_size, struct bpf_call_arg_meta *meta) +{ + enum bpf_access_type type = BPF_READ; + struct dynptr_key_state dynkey; + int err, min_off, max_off; + + err = check_stack_access_within_bounds(env, regno, off, access_size, type); + if (err) + return err; + + err = check_dynkey_stack_access_offset(env, regno, off); + if (err) + return err; + + err = get_stack_access_range(env, regno, off, &min_off, &max_off); + if (err) + return err; + + err = init_dynptr_key_state(env, meta->map_ptr->key_record, &dynkey); + if (err) + return err; + + return check_stack_range_initialized(env, regno, min_off, max_off, access_size, type, + &dynkey); } static int check_helper_mem_access(struct bpf_verifier_env *env, int regno, @@ -9676,18 +9821,33 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, verbose(env, "invalid map_ptr to access map->key\n"); return -EACCES; } + key_size = meta->map_ptr->key_size; - err = check_helper_mem_access(env, regno, key_size, BPF_READ, false, NULL); - if (err) - return err; - if (can_elide_value_nullness(meta->map_ptr->map_type)) { - err = get_constant_map_key(env, reg, key_size, &meta->const_map_key); - if (err < 0) { - meta->const_map_key = -1; - if (err == -EOPNOTSUPP) - err = 0; - else - return err; + /* Only allow PTR_TO_STACK for dynptr-key */ + if (bpf_map_has_dynptr_key(meta->map_ptr)) { + if (base_type(reg->type) != PTR_TO_STACK) { + verbose(env, "map dynptr-key requires stack ptr but got %s\n", + reg_type_str(env, reg->type)); + return -EACCES; + } + err = check_dynkey_stack_range_access(env, regno, reg->off, key_size, meta); + if (err) + return err; + } else { + err = check_helper_mem_access(env, regno, key_size, BPF_READ, false, NULL); + if (err) + return err; + + if (can_elide_value_nullness(meta->map_ptr->map_type)) { + err = get_constant_map_key(env, reg, key_size, + &meta->const_map_key); + if (err < 0) { + meta->const_map_key = -1; + if (err == -EOPNOTSUPP) + err = 0; + else + return err; + } } } break;