From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938424AbdLSD3P (ORCPT ); Mon, 18 Dec 2017 22:29:15 -0500 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:37809 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S938373AbdLSD2f (ORCPT ); Mon, 18 Dec 2017 22:28:35 -0500 X-ME-Sender: From: "Tobin C. Harding" To: kernel-hardening@lists.openwall.com Cc: "Tobin C. Harding" , Steven Rostedt , Tycho Andersen , Linus Torvalds , Kees Cook , Andrew Morton , Daniel Borkmann , Masahiro Yamada , Alexei Starovoitov , linux-kernel@vger.kernel.org, Network Development Subject: [PATCH v2 2/3] vsprintf: print if symbol not found Date: Tue, 19 Dec 2017 14:28:13 +1100 Message-Id: <1513654094-16832-3-git-send-email-me@tobin.cc> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1513654094-16832-1-git-send-email-me@tobin.cc> References: <1513654094-16832-1-git-send-email-me@tobin.cc> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Depends on: commit 40eee173a35e ("kallsyms: don't leak address when symbol not found") Currently vsprintf for specifiers %p[SsB] relies on the behaviour of kallsyms (sprint_symbol()) and prints the actual address if a symbol is not found. Previous patch changes this behaviour so that sprint_symbol() returns an error if symbol not found. With this patch in place we can print a sanitized message '' instead of leaking the address. Print '' for printk specifier %p[sSB] if symbol look up fails. Signed-off-by: Tobin C. Harding --- lib/vsprintf.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 01c3957b2de6..820ed4fe6e6c 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -674,6 +674,8 @@ char *symbol_string(char *buf, char *end, void *ptr, unsigned long value; #ifdef CONFIG_KALLSYMS char sym[KSYM_SYMBOL_LEN]; + const char *sym_not_found = ""; + int ret; #endif if (fmt[1] == 'R') @@ -682,11 +684,14 @@ char *symbol_string(char *buf, char *end, void *ptr, #ifdef CONFIG_KALLSYMS if (*fmt == 'B') - sprint_backtrace(sym, value); + ret = sprint_backtrace(sym, value); else if (*fmt != 'f' && *fmt != 's') - sprint_symbol(sym, value); + ret = sprint_symbol(sym, value); else - sprint_symbol_no_offset(sym, value); + ret = sprint_symbol_no_offset(sym, value); + + if (ret == -1) + strcpy(sym, sym_not_found); return string(buf, end, sym, spec); #else -- 2.7.4