From nobody Tue Nov 26 21:25:03 2024 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 DD7051F9EBD for ; Tue, 15 Oct 2024 23:17:07 +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=1729034230; cv=none; b=ejkkWE59PU/hvhLrSBVIJ3N820Mr76RbUYFzcStstj+snYWQ2PO6Vv7BGgX/adGyxOZ/jDpOYNzB2qctzWWiZQwgGE6h7nxDvzRMmGWYJsDPEAm08P8+HQ0AvSyr1NC0m8DM5aSmWQK4gZ0w+Wt1cp5ORD5cPhW12jP6j/UVf3Y= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729034230; c=relaxed/simple; bh=YE/oK9ZOhdsHNUDoCLONYihU16c/izMFQR3EpE6qWgg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Ira+WerPYsoj04t6TszuQ2i2p0M4GUdn682qVb3MbxRCNF7daem0SjxziekaCUWa/wKnJolGsquL5y/gvPRJXE/mU1ssPYn6j422EIOz4gspHCQPM+FGJs/QcrWSkowBhmw7/CRubfyIUi/xI04cDnSrYHGDoqk4kiYGxHp+JAg= 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=TwwwPg+Z; 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--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="TwwwPg+Z" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-e2904d0cad0so9004312276.1 for ; Tue, 15 Oct 2024 16:17:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1729034227; x=1729639027; 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=hpXqqJ7mhE4OTX7mw0ZIHnsdobY/QXMTdFshJ+hNzmc=; b=TwwwPg+ZV1lFiBZt4WXhSYohJ4VKuSEvF31Vx47EuMkHa+FwmCcvjhXZFfeTxm4o0c EnMvqT3CZDLSPv8vY9g6CP296PScmCdWPOdCuDZg67a07jmbjdI42Eus4UoUJMWs2mcS BS50jFuSGHhphKfHguQ+YRphsVkhW6fQSomgCCBqiLpUpuGy4G+PG1smnbvmiR7XS22b hgyBo/QLC+1XnVRFjwg8kLQdVR1oxHH2kwer0FOYdzk75fjOp4uUzVZBYYyg3Y58yWvN +CTHmvR5YJ1dSWBrpOrAP5GITbOKPBNOvt3sHM+Q6ZKajPIEuHSq7iH81o9/NWHrD3Bp WeXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1729034227; x=1729639027; 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=hpXqqJ7mhE4OTX7mw0ZIHnsdobY/QXMTdFshJ+hNzmc=; b=SgUzqUaGF/1DsvgvniD6e/ANV1SwgiwUPxgaPFtfI3x19tK9t6KqL1XMt5Jl69eqwG gDGcrYhaJL6pIfYQUbsXMeAZZgX62tkzEEDABGecX50iIPUTvPt4BMgq4pN+4Z8ngZrh iMJbHikJEDCbSnTYF/xbXAGiytW8I5LUKQ6j4fz4b6jlAkLsDxlE0qlMrLtBo6hpqapp cAVSjVis6mnC3NyKr4tZCE/MIFnfMW8HE3D1IYDk0JMw6no86lUp9qkYLYlROzhxD0lZ qo4GALdOeJuG5Fxgzz2EK/TPeWjvx7whSutpeW2mCl0MM6Wx8jr1ls02XzylvBfEGiDw QmOw== X-Gm-Message-State: AOJu0Yz4uILMEhLfryQ9ZE1BlQLB8bNDMy0VbRE7mFCF7ieoeppNTYib 1cq/X6mA1z0Dw798b+qFqBi1BDbceKsBJHCc5nQwt+IvsKjgLGZtm7k5AZzZ6EgLVNibr91xsM5 T1T7bIQ== X-Google-Smtp-Source: AGHT+IHizGOPKT5xbBjYB4IekU0DU2Mgds5ptzsICNd3lT/qy4QxEafJXfV6FVd+c7tsCcxLBv+gbqraWgah X-Received: from anyblade.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:1791]) (user=mmaurer job=sendgmr) by 2002:a25:947:0:b0:e29:76b7:ed37 with SMTP id 3f1490d57ef6-e2978585cc5mr1523276.9.1729034226849; Tue, 15 Oct 2024 16:17:06 -0700 (PDT) Date: Tue, 15 Oct 2024 23:16:38 +0000 In-Reply-To: <20241015231651.3851138-1-mmaurer@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241015231651.3851138-1-mmaurer@google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog Message-ID: <20241015231651.3851138-5-mmaurer@google.com> Subject: [PATCH 04/12] module: Factor out elf_validity_cache_secstrings From: Matthew Maurer To: mcgrof@kernel.org Cc: linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org, samitolvanen@google.com, Matthew Maurer , Petr Pavlu , Daniel Gomez Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 467e35f0232a..473f1fb25de2 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -1822,6 +1822,71 @@ static int elf_validity_cache_sechdrs(struct load_in= fo *info) return 0; } =20 +/** + * 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 =3D=3D SHN_UNDEF + || info->hdr->e_shstrndx >=3D info->hdr->e_shnum) { + pr_err("Invalid ELF section name index: %d || e_shstrndx (%d) >=3D e_shn= um (%d)\n", + info->hdr->e_shstrndx, info->hdr->e_shstrndx, + info->hdr->e_shnum); + return -ENOEXEC; + } + + strhdr =3D &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 =3D (void *)info->hdr + strhdr->sh_offset; + if (strhdr->sh_size =3D=3D 0) { + pr_err("empty section name table\n"); + return -ENOEXEC; + } + if (secstrings[strhdr->sh_size - 1] !=3D '\0') { + pr_err("ELF Spec violation: section name table isn't null terminated\n"); + return -ENOEXEC; + } + + for (i =3D 0; i < info->hdr->e_shnum; i++) { + shdr =3D &info->sechdrs[i]; + /* SHT_NULL means sh_name has an undefined value */ + if (shdr->sh_type =3D=3D SHT_NULL) + continue; + if (shdr->sh_name >=3D strhdr->sh_size) { + pr_err("Invalid ELF section name in module (section %u type %u)\n", + i, shdr->sh_type); + return -ENOEXEC; + } + } + + info->secstrings =3D secstrings; + return 0; +} + /* * Check userspace passed ELF module against our expectations, and cache * useful variables for further processing as we go. @@ -1845,7 +1910,7 @@ static int elf_validity_cache_sechdrs(struct load_inf= o *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 =3D 0, mod_idx; unsigned int num_info_secs =3D 0, info_idx; @@ -1854,34 +1919,9 @@ static int elf_validity_cache_copy(struct load_info = *info, int flags) err =3D elf_validity_cache_sechdrs(info); if (err < 0) return err; - - /* - * Verify if the section name table index is valid. - */ - if (info->hdr->e_shstrndx =3D=3D SHN_UNDEF - || info->hdr->e_shstrndx >=3D info->hdr->e_shnum) { - pr_err("Invalid ELF section name index: %d || e_shstrndx (%d) >=3D e_shn= um (%d)\n", - info->hdr->e_shstrndx, info->hdr->e_shstrndx, - info->hdr->e_shnum); - goto no_exec; - } - - strhdr =3D &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 =3D (void *)info->hdr + strhdr->sh_offset; - if (strhdr->sh_size =3D=3D 0) { - pr_err("empty section name table\n"); - goto no_exec; - } - if (info->secstrings[strhdr->sh_size - 1] !=3D '\0') { - pr_err("ELF Spec violation: section name table isn't null terminated\n"); - goto no_exec; - } + err =3D elf_validity_cache_secstrings(info); + if (err < 0) + return err; =20 for (i =3D 1; i < info->hdr->e_shnum; i++) { shdr =3D &info->sechdrs[i]; @@ -1910,14 +1950,6 @@ static int elf_validity_cache_copy(struct load_info = *info, int flags) num_info_secs++; info_idx =3D i; } - - if (shdr->sh_flags & SHF_ALLOC) { - if (shdr->sh_name >=3D strhdr->sh_size) { - pr_err("Invalid ELF section name in module (section %u type %u)\n", - i, shdr->sh_type); - return -ENOEXEC; - } - } break; } } --=20 2.47.0.rc1.288.g06298d1525-goog