From patchwork Thu Apr 18 23:19:47 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Edward Liaw X-Patchwork-Id: 13635508 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8AF027BAFD for ; Thu, 18 Apr 2024 23:20:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713482431; cv=none; b=u+7ZUK0Zyf0nOBMHSfZI9cGHDt2PrqX1VYEmobu44hUDrKDirZKRweEyw0LcBm3t9GPSSsA+/9uHLhqreWYYbPE787QCbQsclSBcdXeIjjvOtpZGrnkueigrdieakpHtHtJuqSPxbkju922k1gulr2tmAyyOcGj1+BrFCR839s4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713482431; c=relaxed/simple; bh=NcUgjEVg58kGwkb+Jw41HUS9kEgKKWzCNIba4ZWXv2A=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=evyaYOWlUsIGSGtENZCopxCVufgnY/xnWYTXxWmYUay0xKkXThPI4nfnxqMUco1JbPFSWP8MWKaYnxVmtO3qtcfvn+PIMhvkNTcnB0aljSABipJRTUwUo+MMtiJ55Z3MmQeDstk0t6FWGKPu8dmCRnCaOcwfyq5Ggkjv/cbcHNI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edliaw.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=P9z5IBeK; arc=none smtp.client-ip=209.85.219.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--edliaw.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="P9z5IBeK" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-de3d9eacb57so2849279276.1 for ; Thu, 18 Apr 2024 16:20:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1713482428; x=1714087228; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=q/YC6vY8cZ2knPVqCxWC6lAFUPFp69AYOLfV73QO6KQ=; b=P9z5IBeK68QY2BLELLAGvRdFsi2RK+7AUtkt+mKbmNAc5qy5Gb77gBezKJiJAsPxV0 Pl2V0QYYH/rSQAJI3tAyPWhPpMUFPbVBUoId+kJGcs3TvWrr88hhMKi6Z/xxQZSKKv3R q60Tcb8g3sxJXsBJY9apGTzi3bcNjouMJW1bnHM9+evADYc08J1NHIiAMbHNJyBaiiI0 4UBT8E6DzbM7JKBlHirdGBJnazosbN78d7R3oFoNpkxg6ctoYnmS1p5B2nCitGxtRPFt j2g+3ioEYqIbPzb7jwvecSUztKfvpcPUmGzbC96KyHa1384IKLoTv/AYrflEev3XnPyo Y21Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713482428; x=1714087228; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=q/YC6vY8cZ2knPVqCxWC6lAFUPFp69AYOLfV73QO6KQ=; b=jMz/mo0izV4YPQ4LswIQ9Q0JuS8E/GhSJYc6imZ69afzKi2IWi+kU44YzwRupJXgDa DxiFowPFeGcw3vLIX1Oea6enf1hcrXgDzf47c709Pf374mGKSOtxhrrFFniJzW8szO/A XilaKeFiycwqqwbXrM4Vj62axKITClPipbDCwv/BMTGf4flYzpa5Z3Qb9OoqZKKCq5f8 0H8IX1fUBAZnU6Pl6ig2BxUzhikB40NJ+gbYnoh0EcyIW/mJTYtmSSEqcv/i3NTEQF8g Yk6hJg/h+R2m+Oe0/R7Gza/KyBsHTAYRihHOk4ic2BExCA3TG8SVs8WTN8mPa69J+4uj PAgA== X-Gm-Message-State: AOJu0YxX2DAvSRSRXFDd7ubgQAGsXPVC3RC5RW+znDS1ArxuBHzMx4Qr Fd95ELpCrMPQpuOmCyC0w0LJPILTXapDF4oOl/TsaSI2P/vguSnSgno35rZrpc9WiQFcxjSZiA9 LyA== X-Google-Smtp-Source: AGHT+IHrxrrNUKm29ldT/oIgtUJU7kmFT8cDAHOqQdXSx4NR3b72oYNNm2fwp/UDMHZjPkZRE+Y5djysHRQ= X-Received: from edliaw.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:305d]) (user=edliaw job=sendgmr) by 2002:a25:fc04:0:b0:dc6:cafd:dce5 with SMTP id v4-20020a25fc04000000b00dc6cafddce5mr91879ybd.12.1713482428464; Thu, 18 Apr 2024 16:20:28 -0700 (PDT) Date: Thu, 18 Apr 2024 23:19:47 +0000 In-Reply-To: <20240418232005.34244-1-edliaw@google.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <16430256912363@kroah.com> <20240418232005.34244-1-edliaw@google.com> X-Mailer: git-send-email 2.44.0.769.g3c40516874-goog Message-ID: <20240418232005.34244-2-edliaw@google.com> Subject: [PATCH 5.15.y v3 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support From: Edward Liaw To: stable@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa Cc: bpf@vger.kernel.org, kernel-team@android.com, Edward Liaw , Yonghong Song , linux-kernel@vger.kernel.org, Kumar Kartikeya Dwivedi X-Patchwork-Delegate: bpf@iogearbox.net Allow passing PTR_TO_CTX, if the kfunc expects a matching struct type, and punt to PTR_TO_MEM block if reg->type does not fall in one of PTR_TO_BTF_ID or PTR_TO_SOCK* types. This will be used by future commits to get access to XDP and TC PTR_TO_CTX, and pass various data (flags, l4proto, netns_id, etc.) encoded in opts struct passed as pointer to kfunc. For PTR_TO_MEM support, arguments are currently limited to pointer to scalar, or pointer to struct composed of scalars. This is done so that unsafe scenarios (like passing PTR_TO_MEM where PTR_TO_BTF_ID of in-kernel valid structure is expected, which may have pointers) are avoided. Since the argument checking happens basd on argument register type, it is not easy to ascertain what the expected type is. In the future, support for PTR_TO_MEM for kfunc can be extended to serve other usecases. The struct type whose pointer is passed in may have maximum nesting depth of 4, all recursively composed of scalars or struct with scalars. Future commits will add negative tests that check whether these restrictions imposed for kfunc arguments are duly rejected by BPF verifier or not. [edliaw: merged with changes from 45ce4b4f90091 ("bpf: Fix crash due to out of bounds access into reg2btf_ids.") and f858c2b2ca04 ("bpf: Fix calling global functions from BPF_PROG_TYPE_EXT programs")] Signed-off-by: Kumar Kartikeya Dwivedi Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20211217015031.1278167-4-memxor@gmail.com (cherry picked from commit 3363bd0cfbb80dfcd25003cd3815b0ad8b68d0ff) Signed-off-by: Edward Liaw --- kernel/bpf/btf.c | 93 +++++++++++++++++++++++++++++++++++++----------- 1 file changed, 73 insertions(+), 20 deletions(-) -- 2.44.0.769.g3c40516874-goog diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 5d4bea53ac1f..77929fd7bcef 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5447,6 +5447,46 @@ static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = { #endif }; +/* Returns true if struct is composed of scalars, 4 levels of nesting allowed */ +static bool __btf_type_is_scalar_struct(struct bpf_verifier_log *log, + const struct btf *btf, + const struct btf_type *t, int rec) +{ + const struct btf_type *member_type; + const struct btf_member *member; + u32 i; + + if (!btf_type_is_struct(t)) + return false; + + for_each_member(i, t, member) { + const struct btf_array *array; + + member_type = btf_type_skip_modifiers(btf, member->type, NULL); + if (btf_type_is_struct(member_type)) { + if (rec >= 3) { + bpf_log(log, "max struct nesting depth exceeded\n"); + return false; + } + if (!__btf_type_is_scalar_struct(log, btf, member_type, rec + 1)) + return false; + continue; + } + if (btf_type_is_array(member_type)) { + array = btf_type_array(member_type); + if (!array->nelems) + return false; + member_type = btf_type_skip_modifiers(btf, array->type, NULL); + if (!btf_type_is_scalar(member_type)) + return false; + continue; + } + if (!btf_type_is_scalar(member_type)) + return false; + } + return true; +} + static int btf_check_func_arg_match(struct bpf_verifier_env *env, const struct btf *btf, u32 func_id, struct bpf_reg_state *regs, @@ -5455,6 +5495,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, enum bpf_prog_type prog_type = env->prog->type == BPF_PROG_TYPE_EXT ? env->prog->aux->dst_prog->type : env->prog->type; struct bpf_verifier_log *log = &env->log; + bool is_kfunc = btf_is_kernel(btf); const char *func_name, *ref_tname; const struct btf_type *t, *ref_t; const struct btf_param *args; @@ -5507,7 +5548,20 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id); ref_tname = btf_name_by_offset(btf, ref_t->name_off); - if (btf_is_kernel(btf)) { + if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) { + /* If function expects ctx type in BTF check that caller + * is passing PTR_TO_CTX. + */ + if (reg->type != PTR_TO_CTX) { + bpf_log(log, + "arg#%d expected pointer to ctx, but got %s\n", + i, btf_type_str(t)); + return -EINVAL; + } + if (check_ctx_reg(env, reg, regno)) + return -EINVAL; + } else if (is_kfunc && (reg->type == PTR_TO_BTF_ID || + (reg2btf_ids[base_type(reg->type)] && !type_flag(reg->type)))) { const struct btf_type *reg_ref_t; const struct btf *reg_btf; const char *reg_ref_tname; @@ -5523,14 +5577,9 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, if (reg->type == PTR_TO_BTF_ID) { reg_btf = reg->btf; reg_ref_id = reg->btf_id; - } else if (reg2btf_ids[base_type(reg->type)]) { + } else { reg_btf = btf_vmlinux; reg_ref_id = *reg2btf_ids[base_type(reg->type)]; - } else { - bpf_log(log, "kernel function %s args#%d expected pointer to %s %s but R%d is not a pointer to btf_id\n", - func_name, i, - btf_type_str(ref_t), ref_tname, regno); - return -EINVAL; } reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id, @@ -5546,22 +5595,24 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, reg_ref_tname); return -EINVAL; } - } else if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) { - /* If function expects ctx type in BTF check that caller - * is passing PTR_TO_CTX. - */ - if (reg->type != PTR_TO_CTX) { - bpf_log(log, - "arg#%d expected pointer to ctx, but got %s\n", - i, btf_type_str(t)); - return -EINVAL; - } - if (check_ctx_reg(env, reg, regno)) - return -EINVAL; } else if (ptr_to_mem_ok) { const struct btf_type *resolve_ret; u32 type_size; + if (is_kfunc) { + /* Permit pointer to mem, but only when argument + * type is pointer to scalar, or struct composed + * (recursively) of scalars. + */ + if (!btf_type_is_scalar(ref_t) && + !__btf_type_is_scalar_struct(log, btf, ref_t, 0)) { + bpf_log(log, + "arg#%d pointer type %s %s must point to scalar or struct with scalar\n", + i, btf_type_str(ref_t), ref_tname); + return -EINVAL; + } + } + resolve_ret = btf_resolve_size(btf, ref_t, &type_size); if (IS_ERR(resolve_ret)) { bpf_log(log, @@ -5574,6 +5625,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, if (check_mem_reg(env, reg, regno, type_size)) return -EINVAL; } else { + bpf_log(log, "reg type unsupported for arg#%d %sfunction %s#%d\n", i, + is_kfunc ? "kernel " : "", func_name, func_id); return -EINVAL; } } @@ -5623,7 +5676,7 @@ int btf_check_kfunc_arg_match(struct bpf_verifier_env *env, const struct btf *btf, u32 func_id, struct bpf_reg_state *regs) { - return btf_check_func_arg_match(env, btf, func_id, regs, false); + return btf_check_func_arg_match(env, btf, func_id, regs, true); } /* Convert BTF of a function into bpf_reg_state if possible