From nobody Tue Mar 11 19:53:40 2025 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (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 D01A51CACD9 for ; Tue, 15 Oct 2024 23:17:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729034227; cv=none; b=YT15f89ObFNQ/jgI4E1BSF/CeTclUNCBZD+61F3dGRjngiKY0gJHHhs1UknQ3T468jqfrEnBCfBknPdzQBcjNJ2CGkb58woFcoBZMC0PQTpahAVO3d1EXnVgfVsBdySbgPP/5fLMBpq6L1Z04XtYe08y5TniFObIOaordTLkTuo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729034227; c=relaxed/simple; bh=Q/ebP4VppKXgX75HHkGyapl6+59q2K1k/6cBCCOTXVg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=YFsjHxM5LlYZcTVxlvxvai6ZKyxi0cPTPzN6UXSDvkqS9I4Skdu7wara6nPtVnnAJ6r3Z2BQf3lz9WnkGBMaOJViO7ZepMOjw1kPgJj2Nwqc+4J+9Fu4NoNsUbuDb8p+C6lqZZKKGumtj2DmjImTLB0ZTa/e1hGiqh0Ff2xnTFA= 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=CfVslK/m; arc=none smtp.client-ip=209.85.219.201 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="CfVslK/m" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-e2928d9e615so6644470276.0 for ; Tue, 15 Oct 2024 16:17:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1729034225; x=1729639025; 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=s9C2Ei02TD++bK2BpkVHJvqSOFvsQEfujDFHeRhGRWA=; b=CfVslK/mQVPkVgi4qJvoUZuABqvmzYgpJ6kTRKUmqxe8S7zCiSW7iob7vGS+xY4cAT SRP68ozJtRNQr795X4nh2LyqiTysn4ptun2+nwfAncPcdaR8r0UNBVdX1/m0KiaTBSQk WNwkJ/frh8rDOPyLEos1bqxVoRBth+TfLH9RZQ8TAYmn7Kqzngd5kSTiU15EX6Ix1l/O dOhtXgts75yCjRl+hehBodMZ7JaWZCp49lRh2rjKYnYgEnVNwxGwiwIqIhgdsg0n7ZEM nH1FXWMknZZ+doIM3pAy5lCDa/DlMp1KSbzDwIVGFM06fxF2uh+VHQcc9OnpOmRh/ytC mzWQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1729034225; x=1729639025; 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=s9C2Ei02TD++bK2BpkVHJvqSOFvsQEfujDFHeRhGRWA=; b=Q0TvyWNCDGBBPY7r7GWJyV8UPrmquqsFTrtUO3JpNCHulU75d+YY0m5RU3O3+oREqA K04V6hotJCq6n8Up92BYEgJSfro2/4EpY38SjQ6wgP4G6N3TSfVbf4AYMEE2nazfnPoX tuP5qW4gUT58hnyWgr64ThYScCwYsDOfMFkoUns2a8Emq8wEgMhmvpk+eRC1hYPEmN8x 3E8YyGhnJQWP/J2e+kKVKGvds++zW7pAmRiGrXrIXqrf3cOr83Cd1Rjb2p/bKCMu5iH8 sXQeghb1rBkJogaLpmI0woesjhjXvW9m2IvMunHRwtOxyYOguqbde5c6zNzQdIhTLw/S pPlg== X-Gm-Message-State: AOJu0YywlLxourgA5VNljdPW7nPikARVE0M36C1rtdpESY1h2cGynNxW uEaSLPxcWHGk+tgw5DnC84tCLOjElYYjOoqO4WD7JeSb1AsQHc3B3Jc/t56tJbpz8V0mj4OnQQe QnhonWg== X-Google-Smtp-Source: AGHT+IF9/RrejyXjamOHmES0fO9LFDxPPSqw0EHrizmRCN81klIy8hyZiM00NmuWFywfdGDutrXWewNuQlb5 X-Received: from anyblade.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:1791]) (user=mmaurer job=sendgmr) by 2002:a25:68d4:0:b0:e29:6fd5:70ec with SMTP id 3f1490d57ef6-e2978558d8dmr2050276.6.1729034224721; Tue, 15 Oct 2024 16:17:04 -0700 (PDT) Date: Tue, 15 Oct 2024 23:16:37 +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: <20241015231651.3851138-4-mmaurer@google.com> Subject: [PATCH 03/12] module: Factor out elf_validity_cache_sechdrs 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 and document the validation of section headers. Because we now validate all section offsets and lengths before accessing them, we can remove the ad-hoc checks. Signed-off-by: Matthew Maurer --- kernel/module/main.c | 125 ++++++++++++++++++++++++++++--------------- 1 file changed, 82 insertions(+), 43 deletions(-) diff --git a/kernel/module/main.c b/kernel/module/main.c index c836354928f0..467e35f0232a 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -1741,6 +1741,87 @@ static int elf_validity_ehdr(const struct load_info = *info) return 0; } =20 +/** + * elf_validity_cache_sechdrs() - Cache section headers if valid + * @info: Load info to compute section headers from + * + * Checks: + * + * * ELF header is valid (see elf_validity_ehdr()) + * * Section headers are the size we expect + * * Section array fits in the user provided data + * * Section index 0 is NULL + * * Section contents are inbounds + * + * Then updates @info with a &load_info->sechdrs pointer if valid. + * + * Return: %0 if valid, negative error code if validation failed. + */ +static int elf_validity_cache_sechdrs(struct load_info *info) +{ + Elf_Shdr *sechdrs; + Elf_Shdr *shdr; + int i; + int err; + + err =3D elf_validity_ehdr(info); + if (err < 0) + return err; + + if (info->hdr->e_shentsize !=3D sizeof(Elf_Shdr)) { + pr_err("Invalid ELF section header size\n"); + return -ENOEXEC; + } + + /* + * e_shnum is 16 bits, and sizeof(Elf_Shdr) is + * known and small. So e_shnum * sizeof(Elf_Shdr) + * will not overflow unsigned long on any platform. + */ + if (info->hdr->e_shoff >=3D info->len + || (info->hdr->e_shnum * sizeof(Elf_Shdr) > + info->len - info->hdr->e_shoff)) { + pr_err("Invalid ELF section header overflow\n"); + return -ENOEXEC; + } + + sechdrs =3D (void *)info->hdr + info->hdr->e_shoff; + + /* + * The code assumes that section 0 has a length of zero and + * an addr of zero, so check for it. + */ + if (sechdrs[0].sh_type !=3D SHT_NULL + || sechdrs[0].sh_size !=3D 0 + || sechdrs[0].sh_addr !=3D 0) { + pr_err("ELF Spec violation: section 0 type(%d)!=3DSH_NULL or non-zero le= n or addr\n", + sechdrs[0].sh_type); + return -ENOEXEC; + } + + /* Validate contents are inbounds */ + for (i =3D 1; i < info->hdr->e_shnum; i++) { + shdr =3D &sechdrs[i]; + switch (shdr->sh_type) { + case SHT_NULL: + case SHT_NOBITS: + /* No contents, offset/size don't mean anything */ + continue; + default: + err =3D validate_section_offset(info, shdr); + if (err < 0) { + pr_err("Invalid ELF section in module (section %u type %u)\n", + i, shdr->sh_type); + return err; + } + } + } + + info->sechdrs =3D sechdrs; + + return 0; +} + /* * Check userspace passed ELF module against our expectations, and cache * useful variables for further processing as we go. @@ -1770,29 +1851,10 @@ static int elf_validity_cache_copy(struct load_info= *info, int flags) unsigned int num_info_secs =3D 0, info_idx; unsigned int num_sym_secs =3D 0, sym_idx; =20 - err =3D elf_validity_ehdr(info); + err =3D elf_validity_cache_sechdrs(info); if (err < 0) return err; =20 - if (info->hdr->e_shentsize !=3D sizeof(Elf_Shdr)) { - pr_err("Invalid ELF section header size\n"); - goto no_exec; - } - - /* - * e_shnum is 16 bits, and sizeof(Elf_Shdr) is - * known and small. So e_shnum * sizeof(Elf_Shdr) - * will not overflow unsigned long on any platform. - */ - if (info->hdr->e_shoff >=3D info->len - || (info->hdr->e_shnum * sizeof(Elf_Shdr) > - info->len - info->hdr->e_shoff)) { - pr_err("Invalid ELF section header overflow\n"); - goto no_exec; - } - - info->sechdrs =3D (void *)info->hdr + info->hdr->e_shoff; - /* * Verify if the section name table index is valid. */ @@ -1805,11 +1867,6 @@ static int elf_validity_cache_copy(struct load_info = *info, int flags) } =20 strhdr =3D &info->sechdrs[info->hdr->e_shstrndx]; - err =3D validate_section_offset(info, strhdr); - if (err < 0) { - pr_err("Invalid ELF section hdr(type %u)\n", strhdr->sh_type); - return err; - } =20 /* * The section name table must be NUL-terminated, as required @@ -1826,18 +1883,6 @@ static int elf_validity_cache_copy(struct load_info = *info, int flags) goto no_exec; } =20 - /* - * The code assumes that section 0 has a length of zero and - * an addr of zero, so check for it. - */ - if (info->sechdrs[0].sh_type !=3D SHT_NULL - || info->sechdrs[0].sh_size !=3D 0 - || info->sechdrs[0].sh_addr !=3D 0) { - pr_err("ELF Spec violation: section 0 type(%d)!=3DSH_NULL or non-zero le= n or addr\n", - info->sechdrs[0].sh_type); - goto no_exec; - } - for (i =3D 1; i < info->hdr->e_shnum; i++) { shdr =3D &info->sechdrs[i]; switch (shdr->sh_type) { @@ -1856,12 +1901,6 @@ static int elf_validity_cache_copy(struct load_info = *info, int flags) sym_idx =3D i; fallthrough; default: - err =3D validate_section_offset(info, shdr); - if (err < 0) { - pr_err("Invalid ELF section in module (section %u type %u)\n", - i, shdr->sh_type); - return err; - } if (strcmp(info->secstrings + shdr->sh_name, ".gnu.linkonce.this_module") =3D=3D 0) { num_mod_secs++; --=20 2.47.0.rc1.288.g06298d1525-goog