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5fdc7db644("module: setup load info before module_sig_check()") moved the ELF setup, so that it was done before the signature check. This made the module name available to signature error messages. However, the checks for ELF correctness in setup_load_info are not sufficient to prevent bad memory references due to corrupted offset fields, indices, etc. So, there's a regression in behavior here: a corrupt and unsigned (or badly signed) module, which might previously have been rejected immediately, can now cause an oops/crash. Harden ELF handling for module loading by doing the following: - Move the signature check back up so that it comes before ELF initialization. It's best to do the signature check to see if we can trust the module, before using the ELF structures inside it. This also makes checks against info->len more accurate again, as this field will be reduced by the length of the signature in mod_check_sig(). The module name is now once again not available for error messages during the signature check, but that seems like a fair tradeoff. - Check if sections have offset / size fields that at least don't exceed the length of the module. - Check if sections have section name offsets that don't fall outside the section name table. - Add a few other sanity checks against invalid section indices, etc. This is not an exhaustive consistency check, but the idea is to at least get through the signature and blacklist checks without crashing because of corrupted ELF info, and to error out gracefully for most issues that would have caused problems later on. Fixes:5fdc7db644("module: setup load info before module_sig_check()") Signed-off-by: Frank van der Linden <fllinden@amazon.com> Signed-off-by: Jessica Yu <jeyu@kernel.org>
47 lines
1.1 KiB
C
47 lines
1.1 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Module signature checker
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*
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* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#include <linux/errno.h>
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#include <linux/printk.h>
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#include <linux/module_signature.h>
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#include <asm/byteorder.h>
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/**
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* mod_check_sig - check that the given signature is sane
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*
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* @ms: Signature to check.
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* @file_len: Size of the file to which @ms is appended.
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* @name: What is being checked. Used for error messages.
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*/
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int mod_check_sig(const struct module_signature *ms, size_t file_len,
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const char *name)
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{
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if (be32_to_cpu(ms->sig_len) >= file_len - sizeof(*ms))
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return -EBADMSG;
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if (ms->id_type != PKEY_ID_PKCS7) {
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pr_err("%s: not signed with expected PKCS#7 message\n",
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name);
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return -ENOPKG;
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}
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if (ms->algo != 0 ||
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ms->hash != 0 ||
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ms->signer_len != 0 ||
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ms->key_id_len != 0 ||
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ms->__pad[0] != 0 ||
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ms->__pad[1] != 0 ||
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ms->__pad[2] != 0) {
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pr_err("%s: PKCS#7 signature info has unexpected non-zero params\n",
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name);
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return -EBADMSG;
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}
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return 0;
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}
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