From owner-freebsd-hackers@freebsd.org Sat Oct 26 17:32:08 2019 Return-Path: Delivered-To: freebsd-hackers@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 6FCEB17AB3B for ; Sat, 26 Oct 2019 17:32:08 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 470p2H0C8Dz4QZq for ; Sat, 26 Oct 2019 17:32:06 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.15.2/8.15.2) with ESMTPS id x9QHVm0K060263 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Sat, 26 Oct 2019 20:31:51 +0300 (EEST) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua x9QHVm0K060263 Received: (from kostik@localhost) by tom.home (8.15.2/8.15.2/Submit) id x9QHVlwL060262; Sat, 26 Oct 2019 20:31:47 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Sat, 26 Oct 2019 20:31:47 +0300 From: Konstantin Belousov To: Cy Schubert Cc: freebsd-hackers@freebsd.org Subject: Re: ASLR and Stack Gap != 0 Message-ID: <20191026173147.GN73312@kib.kiev.ua> References: <201910261728.x9QHS7av001087@slippy.cwsent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201910261728.x9QHS7av001087@slippy.cwsent.com> User-Agent: Mutt/1.12.2 (2019-09-21) X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FROM, NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on tom.home X-Rspamd-Queue-Id: 470p2H0C8Dz4QZq X-Spamd-Bar: - Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=gmail.com (policy=none); spf=softfail (mx1.freebsd.org: 2001:470:d5e7:1::1 is neither permitted nor denied by domain of kostikbel@gmail.com) smtp.mailfrom=kostikbel@gmail.com X-Spamd-Result: default: False [-2.00 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_FROM(0.00)[gmail.com]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; MIME_GOOD(-0.10)[text/plain]; HAS_XAW(0.00)[]; R_SPF_SOFTFAIL(0.00)[~all]; IP_SCORE_FREEMAIL(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; SUBJECT_HAS_EXCLAIM(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; IP_SCORE(0.00)[ip: (-2.65), ipnet: 2001:470::/32(-4.60), asn: 6939(-3.45), country: US(-0.05)]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:6939, ipnet:2001:470::/32, country:US]; RCVD_COUNT_TWO(0.00)[2]; FREEMAIL_ENVFROM(0.00)[gmail.com]; DMARC_POLICY_SOFTFAIL(0.10)[gmail.com : No valid SPF, No valid DKIM,none] X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 26 Oct 2019 17:32:08 -0000 On Sat, Oct 26, 2019 at 10:28:07AM -0700, Cy Schubert wrote: > Let's try this again. This time with a subject line. > > Hi, > > The following little test case segfaults when aslr is enabled: > > #include > #include > #include > #include > > int > main(int argc, char *argv[]) > { > struct rlimit rl; > int rc; > > rl.rlim_cur = 50 * 4096; > rl.rlim_max = 50 * 4096; > rc = setrlimit(RLIMIT_STACK, &rl); > > return(rc); > } > > > slippy# sysctl kern.elf64.aslr.enable=1 > kern.elf64.aslr.enable: 0 -> 1 > slippy# ./test > Segmentation fault (core dumped) > slippy# gdb test > GNU gdb (GDB) 8.3.1 [GDB v8.3.1 for FreeBSD] > Copyright (C) 2019 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later > > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. > Type "show copying" and "show warranty" for details. > This GDB was configured as "x86_64-portbld-freebsd13.0". > Type "show configuration" for configuration details. > For bug reporting instructions, please see: > . > Find the GDB manual and other documentation resources online at: > . > > For help, type "help". > Type "apropos word" to search for commands related to "word"... > Reading symbols from test... > (gdb) run > Starting program: /export/home/cy/freebsd/tests/setrlimit/test > > Program received signal SIGSEGV, Segmentation fault. > setrlimit () at setrlimit.S:4 > 4 setrlimit.S: No such file or directory. > (gdb) bt > #0 setrlimit () at setrlimit.S:4 > Backtrace stopped: Cannot access memory at address 0x7fffffe372e8 > (gdb) > > > It only occurs with aslr enabled and stack gap != 0. This isn't right. > I already explained this, also you might find this written down one more time at https://github.com/freebsd/freebsd-quarterly/blob/master/2019q3/stack_gap.md