From mboxrd@z Thu Jan 1 00:00:00 1970 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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 2C834C3A5A6 for ; Thu, 19 Sep 2019 22:13:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 023B521A49 for ; Thu, 19 Sep 2019 22:13:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568931239; bh=/cJb+htfQAkNd+2fIa/5w62fEqY+y7eBmbzaphFs5TM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=13VctZay0c1IlA/SL82DtLK/zLTTSmvyrNHdEQ+/W/0ulZROHnFoQm0fATRUierDj GJwbzjZBG0bnsm+1FtUsvFUdb9mAsYTC6hd9ynws+mWMvJz+jK6etDcTus/ImZ4htu lO9C4R/g+XBbSjAGeVBuNR9qGjs01Jx4+hJ1fIdc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391903AbfISWNy (ORCPT ); Thu, 19 Sep 2019 18:13:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:53098 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732518AbfISWNw (ORCPT ); Thu, 19 Sep 2019 18:13:52 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 12A7F21928; Thu, 19 Sep 2019 22:13:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568931230; bh=/cJb+htfQAkNd+2fIa/5w62fEqY+y7eBmbzaphFs5TM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xSYLAtWrP3HnOPrXZBKjZS0yN2EwWsjC++t0ecyxJQSTVczllOld55iSHifDGPZms DOt3w1f2hhb7qTv0nH2JifaZWkpSSbSE2TyKeJIcb4/bEhMgvGj/osxJZJWx3ceoyj K5sNIqS6jnZDhjhlb8j/MnySGUJb1r7lMVAhd1Bs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Masami Hiramatsu , Arnaldo Carvalho de Melo , Peter Zijlstra , Will Deacon , Catalin Marinas , Marc Zyngier , Sasha Levin Subject: [PATCH 4.19 51/79] kallsyms: Dont let kallsyms_lookup_size_offset() fail on retrieving the first symbol Date: Fri, 20 Sep 2019 00:03:36 +0200 Message-Id: <20190919214811.975668286@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190919214807.612593061@linuxfoundation.org> References: <20190919214807.612593061@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Marc Zyngier [ Upstream commit 2a1a3fa0f29270583f0e6e3100d609e09697add1 ] An arm64 kernel configured with CONFIG_KPROBES=y CONFIG_KALLSYMS=y # CONFIG_KALLSYMS_ALL is not set CONFIG_KALLSYMS_BASE_RELATIVE=y reports the following kprobe failure: [ 0.032677] kprobes: failed to populate blacklist: -22 [ 0.033376] Please take care of using kprobes. It appears that kprobe fails to retrieve the symbol at address 0xffff000010081000, despite this symbol being in System.map: ffff000010081000 T __exception_text_start This symbol is part of the first group of aliases in the kallsyms_offsets array (symbol names generated using ugly hacks in scripts/kallsyms.c): kallsyms_offsets: .long 0x1000 // do_undefinstr .long 0x1000 // efi_header_end .long 0x1000 // _stext .long 0x1000 // __exception_text_start .long 0x12b0 // do_cp15instr Looking at the implementation of get_symbol_pos(), it returns the lowest index for aliasing symbols. In this case, it return 0. But kallsyms_lookup_size_offset() considers 0 as a failure, which is obviously wrong (there is definitely a valid symbol living there). In turn, the kprobe blacklisting stops abruptly, hence the original error. A CONFIG_KALLSYMS_ALL kernel wouldn't fail as there is always some random symbols at the beginning of this array, which are never looked up via kallsyms_lookup_size_offset. Fix it by considering that get_symbol_pos() is always successful (which is consistent with the other uses of this function). Fixes: ffc5089196446 ("[PATCH] Create kallsyms_lookup_size_offset()") Reviewed-by: Masami Hiramatsu Cc: Arnaldo Carvalho de Melo Cc: Peter Zijlstra Cc: Will Deacon Cc: Catalin Marinas Signed-off-by: Marc Zyngier Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- kernel/kallsyms.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 02a0b01380d8e..ed87dac8378cc 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -262,8 +262,10 @@ int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize, { char namebuf[KSYM_NAME_LEN]; - if (is_ksym_addr(addr)) - return !!get_symbol_pos(addr, symbolsize, offset); + if (is_ksym_addr(addr)) { + get_symbol_pos(addr, symbolsize, offset); + return 1; + } return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) || !!__bpf_address_lookup(addr, symbolsize, offset, namebuf); } -- 2.20.1