From patchwork Tue Mar 23 20:39:36 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 12159263 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 94438C433EB for ; Tue, 23 Mar 2021 20:41:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 84262619CB for ; Tue, 23 Mar 2021 20:41:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233435AbhCWUkf (ORCPT ); Tue, 23 Mar 2021 16:40:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44972 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233465AbhCWUkD (ORCPT ); Tue, 23 Mar 2021 16:40:03 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7A275C061764 for ; Tue, 23 Mar 2021 13:40:02 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id f81so3809443yba.8 for ; Tue, 23 Mar 2021 13:40:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=i1PxfqvHNAZaUSY0Wt2J9hLbKLkB/NragVXsh/CJXkk=; b=r3h1x+fU5lE/E/LEWwengkgZi5PRsX186ijNQ327TMBLawIZY6LBYeXoo+w52nP2gv rF5I2VWq76FFpaCoMspUWvw8qDIKJm1AsH0+oLVk3E9T+doX05a07ZFN00OhJPnaxkmu jxmLG5HZc+yt4wtJhjo3sZUXCMUwF3pZoczzJSo1cNByG2VVWNmY/KAxOvwH7o3TUBYH bGowaPWnFDFXQgdWtgWmUwuCqSOx5f/zwc5Gwk2eWSiXszhRE499K2081dnK0xsNlJj1 /F+vI9niI/hzqmXXXuXFw6fn+8OOPf3ryNNVi941QfjddB4grHq+9+iY1IfzHYtwau73 lqqg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=i1PxfqvHNAZaUSY0Wt2J9hLbKLkB/NragVXsh/CJXkk=; b=ccC+UY+t/XqCAhRruu7wi2AkmoDLWxfDb8q5nHtx0Xu2M02j/Lk/aKngRkW5LyymZO bCN3rD3P/vIR5WZnNa5BX0mn2cUYPLWyD6CPW5PU2t6M+415VoL/pl3pkmrujUaXAPUQ tGpXx6YnN5VZ31MFAUsfK5TcVHwvd1qa7kJYRmsO5paE87yYboS5YPMBnvhsLdv+RFGi P0J3Sa+6v2gg290SHGFl7oSIYcvc6ZMTaokGAqbsEJYS+tMdYfIq6k59BnLVsMZBD67M IjPBXPz20hwLmlGBbZ9O8TtdJdvw9tAeZhJO2Vb6IwUqwx23Kr2qCuLB8aDie/M3nmY+ qm0w== X-Gm-Message-State: AOAM532IB0B6X2gf02BbXjKKrZ5wVNXlPQP3RQidIIygzbsesQWzK/GQ 4rP5uSHRwRcy16nkrUcHJj1lMWzACyFa3mOV3cE= X-Google-Smtp-Source: ABdhPJxSGEWBzQB/5ovI2vIjo7a1D7A+5mPzIG6DfuCWCyGPkoV9bpBY6tsZB7tVHHd6ltUsB02iXZ3BUgMvr1I18/M= X-Received: from samitolvanen1.mtv.corp.google.com ([2620:15c:201:2:e9a3:260d:763b:67dc]) (user=samitolvanen job=sendgmr) by 2002:a25:a166:: with SMTP id z93mr111661ybh.354.1616532001793; Tue, 23 Mar 2021 13:40:01 -0700 (PDT) Date: Tue, 23 Mar 2021 13:39:36 -0700 In-Reply-To: <20210323203946.2159693-1-samitolvanen@google.com> Message-Id: <20210323203946.2159693-8-samitolvanen@google.com> Mime-Version: 1.0 References: <20210323203946.2159693-1-samitolvanen@google.com> X-Mailer: git-send-email 2.31.0.291.g576ba9dcdaf-goog Subject: [PATCH v3 07/17] kallsyms: strip ThinLTO hashes from static functions From: Sami Tolvanen To: Kees Cook Cc: Nathan Chancellor , Nick Desaulniers , Masahiro Yamada , Will Deacon , Jessica Yu , Arnd Bergmann , Tejun Heo , "Paul E. McKenney" , Christoph Hellwig , Peter Zijlstra , bpf@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Sami Tolvanen Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org With CONFIG_CFI_CLANG and ThinLTO, Clang appends a hash to the names of all static functions not marked __used. This can break userspace tools that don't expect the function name to change, so strip out the hash from the output. Suggested-by: Jack Pham Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook --- kernel/kallsyms.c | 55 ++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 50 insertions(+), 5 deletions(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 8043a90aa50e..c851ca0ed357 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -161,6 +161,27 @@ static unsigned long kallsyms_sym_address(int idx) return kallsyms_relative_base - 1 - kallsyms_offsets[idx]; } +#if defined(CONFIG_CFI_CLANG) && defined(CONFIG_LTO_CLANG_THIN) +/* + * LLVM appends a hash to static function names when ThinLTO and CFI are + * both enabled, i.e. foo() becomes foo$707af9a22804d33c81801f27dcfe489b. + * This causes confusion and potentially breaks user space tools, so we + * strip the suffix from expanded symbol names. + */ +static inline bool cleanup_symbol_name(char *s) +{ + char *res; + + res = strrchr(s, '$'); + if (res) + *res = '\0'; + + return res != NULL; +} +#else +static inline bool cleanup_symbol_name(char *s) { return false; } +#endif + /* Lookup the address for this symbol. Returns 0 if not found. */ unsigned long kallsyms_lookup_name(const char *name) { @@ -173,6 +194,9 @@ unsigned long kallsyms_lookup_name(const char *name) if (strcmp(namebuf, name) == 0) return kallsyms_sym_address(i); + + if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0) + return kallsyms_sym_address(i); } return module_kallsyms_lookup_name(name); } @@ -303,7 +327,9 @@ const char *kallsyms_lookup(unsigned long addr, namebuf, KSYM_NAME_LEN); if (modname) *modname = NULL; - return namebuf; + + ret = namebuf; + goto found; } /* See if it's in a module or a BPF JITed image. */ @@ -316,11 +342,16 @@ const char *kallsyms_lookup(unsigned long addr, if (!ret) ret = ftrace_mod_address_lookup(addr, symbolsize, offset, modname, namebuf); + +found: + cleanup_symbol_name(namebuf); return ret; } int lookup_symbol_name(unsigned long addr, char *symname) { + int res; + symname[0] = '\0'; symname[KSYM_NAME_LEN - 1] = '\0'; @@ -331,15 +362,23 @@ int lookup_symbol_name(unsigned long addr, char *symname) /* Grab name */ kallsyms_expand_symbol(get_symbol_offset(pos), symname, KSYM_NAME_LEN); - return 0; + goto found; } /* See if it's in a module. */ - return lookup_module_symbol_name(addr, symname); + res = lookup_module_symbol_name(addr, symname); + if (res) + return res; + +found: + cleanup_symbol_name(symname); + return 0; } int lookup_symbol_attrs(unsigned long addr, unsigned long *size, unsigned long *offset, char *modname, char *name) { + int res; + name[0] = '\0'; name[KSYM_NAME_LEN - 1] = '\0'; @@ -351,10 +390,16 @@ int lookup_symbol_attrs(unsigned long addr, unsigned long *size, kallsyms_expand_symbol(get_symbol_offset(pos), name, KSYM_NAME_LEN); modname[0] = '\0'; - return 0; + goto found; } /* See if it's in a module. */ - return lookup_module_symbol_attrs(addr, size, offset, modname, name); + res = lookup_module_symbol_attrs(addr, size, offset, modname, name); + if (res) + return res; + +found: + cleanup_symbol_name(name); + return 0; } /* Look up a kernel symbol and return it in a text buffer. */