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Tue, 07 Jul 2026 17:44:46 -0700 (PDT) Received: from ezingerman-fedora-PF4V722J.thefacebook.com ([2620:10d:c090:500::2:84e7]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3117483e0a2sm12371054eec.12.2026.07.07.17.44.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 17:44:45 -0700 (PDT) From: Eduard Zingerman To: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org Cc: daniel@iogearbox.net, martin.lau@linux.dev, kernel-team@fb.com, yonghong.song@linux.dev, eddyz87@gmail.com, memxor@gmail.com, Andrii Nakryiko Subject: [PATCH bpf-next 1/2] bpf: remove artificial limitations on pointer types eligable for spilling Date: Tue, 7 Jul 2026 17:44:28 -0700 Message-ID: <20260707-missing-spillable-types-v1-1-44a92121dc41@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260707-missing-spillable-types-v1-0-44a92121dc41@gmail.com> References: <20260707-missing-spillable-types-v1-0-44a92121dc41@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit The verifier loses precision when simulating stack spills for the following register types: - PTR_TO_TP_BUFFER - PTR_TO_INSN - CONST_PTR_TO_DYNPTR These types are not allow-listed in the is_spillable_regtype(), because of that check_stack_write_fixed_off() takes the branch that marks the slots STACK_MISC. There are no technical reasons for this limititation. This commit replaces an explicit list of pointer types in is_spillable_regtype() with explicit list of non-pointer types. The function is renamed to is_pointer_regtype() for clarity. Reported-by: Andrii Nakryiko Suggested-by: Kumar Kartikeya Dwivedi Signed-off-by: Eduard Zingerman --- kernel/bpf/verifier.c | 39 ++++++++------------------------------- 1 file changed, 8 insertions(+), 31 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3193b473762b..51f7965d42e3 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3304,34 +3304,6 @@ static int mark_chain_precision_batch(struct bpf_verifier_env *env, return bpf_mark_chain_precision(env, starting_state, -1, NULL); } -static bool is_spillable_regtype(enum bpf_reg_type type) -{ - switch (base_type(type)) { - case PTR_TO_MAP_VALUE: - case PTR_TO_STACK: - case PTR_TO_CTX: - case PTR_TO_PACKET: - case PTR_TO_PACKET_META: - case PTR_TO_PACKET_END: - case PTR_TO_FLOW_KEYS: - case CONST_PTR_TO_MAP: - case PTR_TO_SOCKET: - case PTR_TO_SOCK_COMMON: - case PTR_TO_TCP_SOCK: - case PTR_TO_XDP_SOCK: - case PTR_TO_BTF_ID: - case PTR_TO_BUF: - case PTR_TO_MEM: - case PTR_TO_FUNC: - case PTR_TO_MAP_KEY: - case PTR_TO_ARENA: - return true; - default: - return false; - } -} - - /* check if register is a constant scalar value */ static bool is_reg_const(struct bpf_reg_state *reg, bool subreg32) { @@ -3345,13 +3317,18 @@ static u64 reg_const_value(struct bpf_reg_state *reg, bool subreg32) return subreg32 ? tnum_subreg(reg->var_off).value : reg->var_off.value; } +static bool is_pointer_regtype(enum bpf_reg_type type) +{ + return type != SCALAR_VALUE && type != NOT_INIT; +} + static bool __is_pointer_value(bool allow_ptr_leaks, const struct bpf_reg_state *reg) { if (allow_ptr_leaks) return false; - return reg->type != SCALAR_VALUE; + return is_pointer_regtype(reg->type); } static void clear_scalar_id(struct bpf_reg_state *reg) @@ -3476,7 +3453,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env, if (value_regno >= 0) reg = &cur->regs[value_regno]; if (!env->bypass_spec_v4) { - bool sanitize = reg && is_spillable_regtype(reg->type); + bool sanitize = reg && is_pointer_regtype(reg->type); for (i = 0; i < size; i++) { u8 type = state->stack[spi].slot_type[(slot - i) % @@ -3517,7 +3494,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env, __mark_reg_known(tmp_reg, insn->imm); tmp_reg->type = SCALAR_VALUE; save_register_state(env, state, spi, tmp_reg, size); - } else if (reg && is_spillable_regtype(reg->type)) { + } else if (reg && is_pointer_regtype(reg->type)) { /* register containing pointer is being spilled into stack */ if (size != BPF_REG_SIZE) { verbose_linfo(env, insn_idx, "; "); -- 2.55.0