From nobody Fri Nov 29 04:32:35 2024 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (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 181061A4E76 for ; Wed, 25 Sep 2024 23:39:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727307571; cv=none; b=XDRPqjt5BQqEy8bZN+OVpLGT9o6d51z7RBPb8f1ZSZixvelaAbcWN/OeoM3TNaTL80jDNe1P0Z0hVjXP0utWJV+UNC8d7ytAE3+OxPcr8fShHVuS6TbYJ235Mr/+EETBPtw+iVwKP5KTgQYYg1HvgGowfb0QhNd5ZE1oJNw3nmc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727307571; c=relaxed/simple; bh=WRBs20XgxXhpGUNzmAuEPSHiJfsMkZEkGfwB5C4b2is=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Fmhdke2DIDrswzSs8F7hNXvABkUyvHCdLkySAgAGdgj3CtRxEL5E/FB39V0tlVB+0+RdNgDp6x4drlNahISABhi2CH5herZk7f6PvPHGA9Dl2ZOFv3wEIYoLgNxVEbqYzuSgDbDoDW53pRBytPVnL8sg/a+9a30TXwMUeDMXz6c= 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=sOdzlmeY; arc=none smtp.client-ip=209.85.128.202 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="sOdzlmeY" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-690404fd230so8029797b3.3 for ; Wed, 25 Sep 2024 16:39:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1727307568; x=1727912368; 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=srrYfI2SZpfKgIsSq8ppkf2FykJu/mFy8hG5tlqb9h4=; b=sOdzlmeY6RY7bpo53PEnQ0YN0/YFAnlXxFf2ZyhVr/9gJ/T37wmWSna16Pm4dszRsH kCAibe8ECqUZozUmaxsJJ7+d2Dm5yeCNVIMbcVZ+mVHroq8zknRXG3i+PN0xMk0cBaAl KtHEwtBf/e0CK81PJDy1xFIO7XAHMNhTiQ2W/9CFH6eGGuFnl7J0a8aKwnum5Tbv3opT H9UqkbO+NemXGkTfLdo2ya2prR7OXRr+P0NBt/iqNlFXgahpRb5JTkG+yUnuAWhTJFTw LSeXIBkWlkFlvXCLqZPkHXV+roqA0hPB8PmXdgVn9JfShCTD4kB4LdafGD5WjtOjCYBu ZXSg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727307568; x=1727912368; 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=srrYfI2SZpfKgIsSq8ppkf2FykJu/mFy8hG5tlqb9h4=; b=OPCa//ndTPdetULq7gr45Vv/wpOq9eqvv6pjzxgB1S9g9YBJ1K8g53SEuNvjkCzkSs 3i2HqZEYATAJugXtjFFhhUKYkdSm941ZahNEzMyHdx5lluLOeGXyFRsEEmQM2jjbwQx8 Fcgxl8VDiOj+tahaVw3IPAMANuRuRhst5LfoLjaRza56rRMI2d6ZmZVhrT4GFwlIIWSO 0Mt4PN3s1af1tY3Du5OnUvDZv450Tp6ZshtDu/b3/vIXEUpl54CxUqg0h6DXPh5f/UOs Euqr16e49bGWRBiISV6O9f49b3o4EokXqRDzn8hL4AwYviX1Xkn4VdAGQSYloXy7J1/s YI/Q== X-Forwarded-Encrypted: i=1; AJvYcCUglfliz2NgOQObSRahHrRmhMVZerZy4FORm/vw+6G6gqrayuCo0DlBK2lnuYaeAnjJJu/y84O5m+Q7pac=@vger.kernel.org X-Gm-Message-State: AOJu0YwO2luJEnjd7GblVVABS4Zw8wRIjpJ9HgFm+p43U3ydSRbCfh3i SjTS1bj0PghGOQ5+LJHIzywUuctz7/ucD+vNA6zp8V8ZtqYbrl+MNhikWKNNy19sWnGxS6xcnfh cZQiyVw== X-Google-Smtp-Source: AGHT+IFULUhyTdpe6K1NKJ4iYoAXDGeSnRiSbmRLHEzsKyUqZwAanm3jLnuYHrgujVpMDbLQEh9f4w7q22Vi X-Received: from anyblade.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:1791]) (user=mmaurer job=sendgmr) by 2002:a05:690c:c9c:b0:6b0:d571:3540 with SMTP id 00721157ae682-6e21da796e6mr397427b3.6.1727307567956; Wed, 25 Sep 2024 16:39:27 -0700 (PDT) Date: Wed, 25 Sep 2024 23:38:18 +0000 In-Reply-To: <20240925233854.90072-1-mmaurer@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240925233854.90072-1-mmaurer@google.com> X-Mailer: git-send-email 2.46.1.824.gd892dcdcdd-goog Message-ID: <20240925233854.90072-4-mmaurer@google.com> Subject: [PATCH v5 03/16] module: Factor out elf_validity_cache_sechdrs From: Matthew Maurer To: masahiroy@kernel.org, ndesaulniers@google.com, ojeda@kernel.org, gary@garyguo.net, mcgrof@kernel.org, Alex Gaynor Cc: 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, linux-modules@vger.kernel.org, Matthew Maurer , Petr Pavlu , Sami Tolvanen , Daniel Gomez , Boqun Feng , "=?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?=" , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross 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 59c977acfb44..1f3a07ee59c6 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -1708,6 +1708,87 @@ 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. @@ -1737,29 +1818,10 @@ 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. */ @@ -1772,11 +1834,6 @@ 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 @@ -1793,18 +1850,6 @@ 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) { @@ -1823,12 +1868,6 @@ 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 2.46.1.824.gd892dcdcdd-goog