From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751481AbeFEInl (ORCPT ); Tue, 5 Jun 2018 04:43:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:37642 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751354AbeFEInj (ORCPT ); Tue, 5 Jun 2018 04:43:39 -0400 From: Jessica Yu To: linux-kernel@vger.kernel.org Cc: Josh Poimboeuf , live-patching@vger.kernel.org, Jessica Yu Subject: [PATCH] module: exclude SHN_UNDEF symbols from kallsyms api Date: Tue, 5 Jun 2018 10:42:23 +0200 Message-Id: <20180605084223.20556-1-jeyu@kernel.org> X-Mailer: git-send-email 2.16.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Livepatch modules are special in that we preserve their entire symbol tables in order to be able to apply relocations after module load. The unwanted side effect of this is that undefined (SHN_UNDEF) symbols of livepatch modules are accessible via the kallsyms api and this can confuse symbol resolution in livepatch (klp_find_object_symbol()) and cause subtle bugs in livepatch. Have the module kallsyms api skip over SHN_UNDEF symbols. These symbols are usually not available for normal modules anyway as we cut down their symbol tables to just the core (non-undefined) symbols, so this should really just affect livepatch modules. Note that this patch doesn't affect the display of undefined symbols in /proc/kallsyms. Reported-by: Josh Poimboeuf Tested-by: Josh Poimboeuf Signed-off-by: Jessica Yu --- kernel/module.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/module.c b/kernel/module.c index c9bea7f2b43e..dfa61490b37d 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -4070,7 +4070,7 @@ static unsigned long mod_find_symname(struct module *mod, const char *name) for (i = 0; i < kallsyms->num_symtab; i++) if (strcmp(name, symname(kallsyms, i)) == 0 && - kallsyms->symtab[i].st_info != 'U') + kallsyms->symtab[i].st_shndx != SHN_UNDEF) return kallsyms->symtab[i].st_value; return 0; } @@ -4116,6 +4116,10 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *, if (mod->state == MODULE_STATE_UNFORMED) continue; for (i = 0; i < kallsyms->num_symtab; i++) { + + if (kallsyms->symtab[i].st_shndx == SHN_UNDEF) + continue; + ret = fn(data, symname(kallsyms, i), mod, kallsyms->symtab[i].st_value); if (ret != 0) -- 2.16.3