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=-11.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 E7875C433E3 for ; Thu, 23 Jul 2020 15:44:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C392D2063A for ; Thu, 23 Jul 2020 15:44:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FQx0BKIa" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729588AbgGWPoa (ORCPT ); Thu, 23 Jul 2020 11:44:30 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:34683 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727108AbgGWPoa (ORCPT ); Thu, 23 Jul 2020 11:44:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595519068; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=BkBtUhmwfYQ1105zjfG6oXxQ3Lr6xBv5QKA0bUwDU1s=; b=FQx0BKIa3uc19Inr/nrDo7PlQBTNi2GqfBRxFrX4+I6PpSacN9GoAS2Xs30ZE+Dqq/8ub1 AXjjJ/Zm0YiE0HG5/tDFmcw1OoPlknAqJ6O3oFm0/lJoAjdLISjexYKS4cmauFU6Kg7+qh BkhZzZxRhZBGZrKRnk5nwoVVTWdpr3M= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-211-fMTt5sBmMy2_WxbLBXHRrg-1; Thu, 23 Jul 2020 11:44:24 -0400 X-MC-Unique: fMTt5sBmMy2_WxbLBXHRrg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 48BD9100A8C1; Thu, 23 Jul 2020 15:44:23 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.194.249]) by smtp.corp.redhat.com (Postfix) with SMTP id 84FC675563; Thu, 23 Jul 2020 15:44:21 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 23 Jul 2020 17:44:22 +0200 (CEST) Date: Thu, 23 Jul 2020 17:44:20 +0200 From: Oleg Nesterov To: Ingo Molnar , Steven Rostedt Cc: Aaron Merey , Peter Zijlstra , Srikar Dronamraju , linux-kernel@vger.kernel.org Subject: [PATCH] uprobes: change handle_swbp() to send SIGTRAP with si_code=SI_KERNEL Message-ID: <20200723154420.GA32043@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a tracee is uprobed and it hits int3 inserted by debugger, handle_swbp() does send_sig(SIGTRAP, current, 0) which means si_code == SI_USER. This used to work when this code was written, but then GDB started to validate si_code and now it simply can't use breakpoints if the tracee has an active uprobe: # cat test.c void unused_func(void) { } int main(void) { return 0; } # gcc -g test.c -o test # perf probe -x ./test -a unused_func # perf record -e probe_test:unused_func gdb ./test -ex run GNU gdb (GDB) 10.0.50.20200714-git ... Program received signal SIGTRAP, Trace/breakpoint trap. 0x00007ffff7ddf909 in dl_main () from /lib64/ld-linux-x86-64.so.2 (gdb) The tracee hits the internal breakpoint inserted by GDB to monitor shared library events but GDB misinterprets this SIGTRAP and reports a signal. Change handle_swbp() to use force_sig(SIGTRAP), this matches do_int3_user() and fixes the problem. This is the minimal fix for -stable, arch/x86/kernel/uprobes.c is equally wrong; it should use send_sigtrap(TRAP_TRACE) instead of send_sig(SIGTRAP), but this doesn't confuse GDB and needs another x86-specific patch. Reported-by: Aaron Merey Cc: stable@vger.kernel.org Signed-off-by: Oleg Nesterov --- kernel/events/uprobes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index bb0862873dba..5f8b0c52fd2e 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2199,7 +2199,7 @@ static void handle_swbp(struct pt_regs *regs) if (!uprobe) { if (is_swbp > 0) { /* No matching uprobe; signal SIGTRAP. */ - send_sig(SIGTRAP, current, 0); + force_sig(SIGTRAP); } else { /* * Either we raced with uprobe_unregister() or we can't -- 2.25.1.362.g51ebf55