From patchwork Tue Aug 6 21:20:30 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Maurer X-Patchwork-Id: 13755316 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (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 B711717334E for ; Tue, 6 Aug 2024 21:21:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722979281; cv=none; b=GFUnNYMFEJGZOrXdJU8vQbUo4UiIbaf5bZGXAcYy5degFLkCOGUaX9OUqhwDgRkbnJmx6Ro5amuwCScz4CGbSV9BTfjrVzyOwPNcrx/K9L47zw8eRxxxqNRD1Wfd2Xb/g/B13un3z1DX+PsAzNnfiuWd7y/aWfMryt32Zjcdp00= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722979281; c=relaxed/simple; bh=4E3+yqfPZ/EBjg1eFYj7cU9eN58K80vEwUneq+XxFn0=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=KNDG5HT+g4dhaSi9QS/Y5jogZQU1P0lEJzJC4Z6xTZQl2zxBVBdVz7cabMC2rsucj4qs2Kx0JbMcOMSY1seAIalHC9UeM5sSQNZ2yXMPcOycp0MuTpMF/LwbUkkL75AqirUNMX7qInpNAVZjgTqH3o94TKte0wTaqlmKGUHIClA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--mmaurer.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=abKFV/KQ; arc=none smtp.client-ip=209.85.128.201 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--mmaurer.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="abKFV/KQ" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-66628e9ec89so25176847b3.1 for ; Tue, 06 Aug 2024 14:21:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1722979279; x=1723584079; 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=LHlE/ML+MCLjX3kG65evZzMkMroBjJFNmRaVRMV6Lgg=; b=abKFV/KQGWyKxuN54FnqHVJS2pMIzFrZq/tZaeESQkrEgRKULp6UHccJS82T1SA62t 6wifCSSJhB0VFDIGjgRCxBE1S+qhdrb2YeH+W5JzKxeT1s2aHPp4zMDdkU8RYD3L19zx QvWUDmMp57nL8vMPIF/CTl8eUqotLz8v+h3zKdvlbVVLsbaxVCvooFqx2/Rk/6mvuMP1 JbvGPXesxUIYIN4ZI+Yatyr5qVmG27dFmOzp/YjUu8zVk188pjyia56Cw2W6gsCmWv1j DulAt9wosw7xqq4UOGNwl8YdjttrFMRCZdgyfzQPDCcSp4YRcw0D6Mj/fbavqsuhKMrf 7HSg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722979279; x=1723584079; 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=LHlE/ML+MCLjX3kG65evZzMkMroBjJFNmRaVRMV6Lgg=; b=dlNo1jTqR5hi43adCXloYu+jREwZDdJ1o1h82je9QTGUzjtjzhr9QzGQWgqaoA8vvu WfzOSeMYcR9gi1c8T9azRiTV8otsnLtedhRWiPYcjGKaB5oHifOWY79T8svSw87s+2gP yHSyoKkSJmvxro58+pnTTPJ8grrWOm/WLyWQxGGSTiwDdKmVVRqiuJu/tgdybSeNl2Mb 4ixCQ889QppxGhdwOG1vZntxBu8VMZzqpdHy4WkmZnAMSTTdwOmj/flusGJT5SaQDXSD lsGyTeehloVk5Eoy0XHq9DASZ/32i67AaN2WJ/zHsKE7jD6PB/+Xcuc5D61j7v0HfU7E h8EA== X-Forwarded-Encrypted: i=1; AJvYcCX5rwg+GYdp/WdQdlZQ5RbxoxxvXRI+76mX3BtFj2VeO2IJILiGdU5bZ/CqsOL1Q1iShMIA5dFL4OJOq86hWgczGLzS5e1v8xlAwnSCpw== X-Gm-Message-State: AOJu0YyTLQzNKXbX33Q6cIcAK4vOprDkpS3Zlp34shViCj620f/TBo0V 8axLv875H2rZhfOkyQZGxMTxhQRZtlpSVQNh2MMpF+ckNU1HQu0BPbj58Nh/b3Zyee2/2l5TqDq SOX+GeQ== X-Google-Smtp-Source: AGHT+IHs8BjEFP03/hjkSlIFZUQ8Ej9UCuITL4bX8GerqO4z8Xhbdq0f/kQGsTvhAsALlLcsV8i31UDjpw7A X-Received: from anyblade.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:1791]) (user=mmaurer job=sendgmr) by 2002:a05:690c:289:b0:681:8b2d:81ae with SMTP id 00721157ae682-68964d4d4cemr6090117b3.9.1722979278870; Tue, 06 Aug 2024 14:21:18 -0700 (PDT) Date: Tue, 6 Aug 2024 21:20:30 +0000 In-Reply-To: <20240806212106.617164-1-mmaurer@google.com> Precedence: bulk X-Mailing-List: linux-modules@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240806212106.617164-1-mmaurer@google.com> X-Mailer: git-send-email 2.46.0.rc2.264.g509ed76dc8-goog Message-ID: <20240806212106.617164-5-mmaurer@google.com> Subject: [PATCH v3 04/16] module: Factor out elf_validity_cache_secstrings From: Matthew Maurer To: masahiroy@kernel.org, ndesaulniers@google.com, ojeda@kernel.org, gary@garyguo.net, mcgrof@kernel.org, Alex Gaynor , Wedson Almeida Filho Cc: Matthew Maurer , rust-for-linux@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, neal@gompa.dev, marcan@marcan.st, j@jannau.net, asahi@lists.linux.dev, Boqun Feng , " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " , Benno Lossin , Andreas Hindborg , Alice Ryhl , linux-modules@vger.kernel.org Factor out the validation of section names. There are two behavioral changes: 1. Previously, we did not validate non-SHF_ALLOC sections. This may have once been safe, as find_sec skips non-SHF_ALLOC sections, but find_any_sec, which will be used to load BTF if that is enabled, ignores the SHF_ALLOC flag. Since there's no need to support invalid section names, validate all of them, not just SHF_ALLOC sections. 2. Section names were validated *after* accessing them for the purposes of detecting ".modinfo" and ".gnu.linkonce.this_module". They are now checked prior to the access, which could avoid bad accesses with malformed modules. Signed-off-by: Matthew Maurer --- kernel/module/main.c | 106 ++++++++++++++++++++++++++++--------------- 1 file changed, 69 insertions(+), 37 deletions(-) diff --git a/kernel/module/main.c b/kernel/module/main.c index c480fd33861a..252cfa9eee67 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -1789,6 +1789,71 @@ static int elf_validity_cache_sechdrs(struct load_info *info) return 0; } +/** + * elf_validity_cache_secstrings() - Caches section names if valid + * @info: Load info to cache section names from. Must have valid sechdrs. + * + * Specifically checks: + * + * * Section name table index is inbounds of section headers + * * Section name table is not empty + * * Section name table is NUL terminated + * * All section name offsets are inbounds of the section + * + * Then updates @info with a &load_info->secstrings pointer if valid. + * + * Return: %0 if valid, negative error code if validation failed. + */ +static int elf_validity_cache_secstrings(struct load_info *info) +{ + Elf_Shdr *strhdr, *shdr; + char *secstrings; + int i; + + /* + * Verify if the section name table index is valid. + */ + if (info->hdr->e_shstrndx == SHN_UNDEF + || info->hdr->e_shstrndx >= info->hdr->e_shnum) { + pr_err("Invalid ELF section name index: %d || e_shstrndx (%d) >= e_shnum (%d)\n", + info->hdr->e_shstrndx, info->hdr->e_shstrndx, + info->hdr->e_shnum); + return -ENOEXEC; + } + + strhdr = &info->sechdrs[info->hdr->e_shstrndx]; + + /* + * The section name table must be NUL-terminated, as required + * by the spec. This makes strcmp and pr_* calls that access + * strings in the section safe. + */ + secstrings = (void *)info->hdr + strhdr->sh_offset; + if (strhdr->sh_size == 0) { + pr_err("empty section name table\n"); + return -ENOEXEC; + } + if (secstrings[strhdr->sh_size - 1] != '\0') { + pr_err("ELF Spec violation: section name table isn't null terminated\n"); + return -ENOEXEC; + } + + for (i = 0; i < info->hdr->e_shnum; i++) { + shdr = &info->sechdrs[i]; + /* SHT_NULL means sh_name has an undefined value */ + if (shdr->sh_type == SHT_NULL) + continue; + if (shdr->sh_name >= strhdr->sh_size) { + pr_err("Invalid ELF section name in module (section %u type %u)\n", + i, shdr->sh_type); + return -ENOEXEC; + } + } + + info->secstrings = secstrings; + return 0; +} + /* * Check userspace passed ELF module against our expectations, and cache * useful variables for further processing as we go. @@ -1812,7 +1877,7 @@ static int elf_validity_cache_sechdrs(struct load_info *info) static int elf_validity_cache_copy(struct load_info *info, int flags) { unsigned int i; - Elf_Shdr *shdr, *strhdr; + Elf_Shdr *shdr; int err; unsigned int num_mod_secs = 0, mod_idx; unsigned int num_info_secs = 0, info_idx; @@ -1821,34 +1886,9 @@ static int elf_validity_cache_copy(struct load_info *info, int flags) err = elf_validity_cache_sechdrs(info); if (err < 0) return err; - - /* - * Verify if the section name table index is valid. - */ - if (info->hdr->e_shstrndx == SHN_UNDEF - || info->hdr->e_shstrndx >= info->hdr->e_shnum) { - pr_err("Invalid ELF section name index: %d || e_shstrndx (%d) >= e_shnum (%d)\n", - info->hdr->e_shstrndx, info->hdr->e_shstrndx, - info->hdr->e_shnum); - goto no_exec; - } - - strhdr = &info->sechdrs[info->hdr->e_shstrndx]; - - /* - * The section name table must be NUL-terminated, as required - * by the spec. This makes strcmp and pr_* calls that access - * strings in the section safe. - */ - info->secstrings = (void *)info->hdr + strhdr->sh_offset; - if (strhdr->sh_size == 0) { - pr_err("empty section name table\n"); - goto no_exec; - } - if (info->secstrings[strhdr->sh_size - 1] != '\0') { - pr_err("ELF Spec violation: section name table isn't null terminated\n"); - goto no_exec; - } + err = elf_validity_cache_secstrings(info); + if (err < 0) + return err; for (i = 1; i < info->hdr->e_shnum; i++) { shdr = &info->sechdrs[i]; @@ -1877,14 +1917,6 @@ static int elf_validity_cache_copy(struct load_info *info, int flags) num_info_secs++; info_idx = i; } - - if (shdr->sh_flags & SHF_ALLOC) { - if (shdr->sh_name >= strhdr->sh_size) { - pr_err("Invalid ELF section name in module (section %u type %u)\n", - i, shdr->sh_type); - return -ENOEXEC; - } - } break; } }