From nobody Sun Feb 8 11:44:28 2026 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (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 19F3D7E0EB for ; Thu, 18 Apr 2024 23:20:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713482438; cv=none; b=ni6wov4t2Fk3rS29UEapSNYFTH1bRtkhS9RtNVwbK/+6gpXts9kLP8P4DLfuhpIPXr4bSTyZSwV7ANY+Kv3f/fDkss/PEO60gfHeK8xVVrowNYTDVLwKZwpr+kJr2ntf32qMj8xBjcjyCNaPn8AxoLlbXlFTkaumZOZbHd1yplE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713482438; c=relaxed/simple; bh=YScO9mwjaHbzHT2vhYW5LqoeHviUzo+lvVpjgG9XQ3k=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=iUrUAeV35qLdo5MvStJIAmWAVjyOCLsYe/q2jCTJSHL6pMxEoJPoPVvmYvL29svytFhdbt5a2gJi2fTgIAFTam5Ousz0wqJPrCNVzXPboLEAzTt8UsnSdG4+D1C5v1gNIWn3C/X5TlOgZL/yJb+oPhYDXEN9Q87UkMA5eAFEMSY= 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=it1g4hNp; arc=none smtp.client-ip=209.85.216.73 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="it1g4hNp" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-2a4b48d7a19so1338265a91.1 for ; Thu, 18 Apr 2024 16:20:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1713482436; x=1714087236; 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=ntuKGIhl78pmHpDhVuljrWxMFgXG8nBQtJyZ9nYPDms=; b=it1g4hNp5Ye5qfYuW65zW8uvK0L6dEJ3uvlUK0L7gUqk33IndCQLQbDV+gGqxx+mYk TtunhcYOjysRW3f4qQOOFzKymnrizD1uSM99FjxkuejmOQ8vVVCgoDA6roLcvF4P2wFq g9Jskq54AdT11spq3Y+parmkFFC5jt8iRN3y1gyxSw3pE23Vl+ytU/K8hBcr7ZPDOxwk 1Hmf9lui5dUG1Sm1wPfL0OPXwMOBWHfuYOMOx/8+jPhK2oG9bO35R/i1mkE4R+3bhNcZ ODSSKk1Wwt1ozOsB5qCz77QrkrShZczi+4QMlxlmmFg5w2CaRjuR4k+yxnHEZv+TiN6O dxAg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713482436; x=1714087236; 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=ntuKGIhl78pmHpDhVuljrWxMFgXG8nBQtJyZ9nYPDms=; b=JRVQtdnEIyc/+IlvV2yI2du9pCFzdcT4VMYfuu3pSjS72Hy0g915W6djRzkL69H0Ql /I/e3emBCV4stxkI1e7E6hc5ZSyHAlkbsHixuDRdqcDX7fDnqnmzbJ+zlP79R52h+l1o jOrewsrQ4Jc0iogsnLy/VWV9q+MLzC5gxAPuH1UpYJESsIDaKn1JbujLYDliHfqKUS4n hTmintOkFl4KR+p41QUCDEM7mkNbXRtBTSRcJEQPWsK8O4tElCUIV3NNiInzCmlmRdwT FQhYG7OnH0cMFvXSXN2iTFucxsyVVQ9D4+1B69J5eSTzCqFpazoUpPpc/vJJEjH8UOjK oe/A== X-Forwarded-Encrypted: i=1; AJvYcCXw3cZi9OSf6JoIgTaUYzZbHfXNhD5BukrXIibnz0gqT73oFYJ9YeiCIE4WZ/j26UxPbBgFIr4JSGu6sOwAbf45I1deGAP87ZAKQbl/ X-Gm-Message-State: AOJu0YwxBeAb+15phfN9A1UsI+Ltrt/OjjfK7V0zxpHrt/DhV3EPWCI/ SJQvjbTSxeK3E2svKO048vBRjpTY2peTUu24qf/pxKYVgyBNR1ot3MVJMOXVZ3DrRPmEsEU3Stg RSw== X-Google-Smtp-Source: AGHT+IGX3+sK2ZbRibyfYYT7GKwhF6+fOJueP20+WYShxN73szU+fckNs7zUrZwu4bQuzEjoGpGQlExREJI= X-Received: from edliaw.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:305d]) (user=edliaw job=sendgmr) by 2002:a17:90a:8a96:b0:2aa:ab39:fcb6 with SMTP id x22-20020a17090a8a9600b002aaab39fcb6mr8739pjn.1.1713482436246; Thu, 18 Apr 2024 16:20:36 -0700 (PDT) Date: Thu, 18 Apr 2024 23:19:49 +0000 In-Reply-To: <20240418232005.34244-1-edliaw@google.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20240418232005.34244-4-edliaw@google.com> Subject: [PATCH 5.15.y v3 3/5] bpf: Generally fix helper register offset check 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 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Daniel Borkmann Right now the assertion on check_ptr_off_reg() is only enforced for register types PTR_TO_CTX (and open coded also for PTR_TO_BTF_ID), however, this is insufficient since many other PTR_TO_* register types such as PTR_TO_FUNC do not handle/expect register offsets when passed to helper functions. Given this can slip-through easily when adding new types, make this an expl= icit allow-list and reject all other current and future types by default if this= is encountered. Also, extend check_ptr_off_reg() to handle PTR_TO_BTF_ID as well instead of duplicating it. For PTR_TO_BTF_ID, reg->off is used for BTF to match expect= ed BTF ids if struct offset is used. This part still needs to be allowed, but = the dynamic off from the tnum must be rejected. Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") Fixes: eaa6bcb71ef6 ("bpf: Introduce bpf_per_cpu_ptr()") Signed-off-by: Daniel Borkmann Acked-by: John Fastabend Acked-by: Alexei Starovoitov (cherry picked from commit 6788ab23508bddb0a9d88e104284922cb2c22b77) Signed-off-by: Edward Liaw --- kernel/bpf/verifier.c | 39 ++++++++++++++++++++++++++++----------- 1 file changed, 28 insertions(+), 11 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 6fe805b559c0..8cd265d1df34 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3980,14 +3980,15 @@ static int get_callee_stack_depth(struct bpf_verifi= er_env *env, } #endif =20 -int check_ptr_off_reg(struct bpf_verifier_env *env, - const struct bpf_reg_state *reg, int regno) +static int __check_ptr_off_reg(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, int regno, + bool fixed_off_ok) { /* Access to this pointer-typed register or passing it to a helper * is only allowed in its original, unmodified form. */ =20 - if (reg->off) { + if (!fixed_off_ok && reg->off) { verbose(env, "dereference of modified %s ptr R%d off=3D%d disallowed\n", reg_type_str(env, reg->type), regno, reg->off); return -EACCES; @@ -4005,6 +4006,12 @@ int check_ptr_off_reg(struct bpf_verifier_env *env, return 0; } =20 +int check_ptr_off_reg(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, int regno) +{ + return __check_ptr_off_reg(env, reg, regno, false); +} + static int __check_buffer_access(struct bpf_verifier_env *env, const char *buf_info, const struct bpf_reg_state *reg, @@ -5267,12 +5274,6 @@ static int check_reg_type(struct bpf_verifier_env *e= nv, u32 regno, kernel_type_name(btf_vmlinux, *arg_btf_id)); return -EACCES; } - - if (!tnum_is_const(reg->var_off) || reg->var_off.value) { - verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset= \n", - regno); - return -EACCES; - } } =20 return 0; @@ -5327,10 +5328,26 @@ static int check_func_arg(struct bpf_verifier_env *= env, u32 arg, if (err) return err; =20 - if (type =3D=3D PTR_TO_CTX) { - err =3D check_ptr_off_reg(env, reg, regno); + switch ((u32)type) { + case SCALAR_VALUE: + /* Pointer types where reg offset is explicitly allowed: */ + case PTR_TO_PACKET: + case PTR_TO_PACKET_META: + case PTR_TO_MAP_KEY: + case PTR_TO_MAP_VALUE: + case PTR_TO_MEM: + case PTR_TO_MEM | MEM_RDONLY: + case PTR_TO_BUF: + case PTR_TO_BUF | MEM_RDONLY: + case PTR_TO_STACK: + break; + /* All the rest must be rejected: */ + default: + err =3D __check_ptr_off_reg(env, reg, regno, + type =3D=3D PTR_TO_BTF_ID); if (err < 0) return err; + break; } =20 skip_type_check: --=20 2.44.0.769.g3c40516874-goog