From owner-freebsd-current@freebsd.org Wed Nov 28 17:57:26 2018 Return-Path: Delivered-To: freebsd-current@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 264D411380A9 for ; Wed, 28 Nov 2018 17:57:26 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org [IPv6:2001:1900:2254:206a::50:5]) by mx1.freebsd.org (Postfix) with ESMTP id 936587F8BA for ; Wed, 28 Nov 2018 17:57:25 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: by mailman.ysv.freebsd.org (Postfix) id 563C511380A8; Wed, 28 Nov 2018 17:57:25 +0000 (UTC) Delivered-To: current@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 30B1811380A7 for ; Wed, 28 Nov 2018 17:57:25 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 6B1917F8B9 for ; Wed, 28 Nov 2018 17:57:24 +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 wASHv9Gv066081 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 28 Nov 2018 19:57:12 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua wASHv9Gv066081 Received: (from kostik@localhost) by tom.home (8.15.2/8.15.2/Submit) id wASHv8TK066080; Wed, 28 Nov 2018 19:57:08 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Wed, 28 Nov 2018 19:57:08 +0200 From: Konstantin Belousov To: Peter Holm Cc: Vladimir Kondratyev , current@freebsd.org Subject: Re: r340343 triggers kernel assertion if file is opened with O_BENEATH flag set through symlink Message-ID: <20181128175708.GI2378@kib.kiev.ua> References: <20181127234617.GE2378@kib.kiev.ua> <20181128095059.GA13602@x2.osted.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20181128095059.GA13602@x2.osted.lan> User-Agent: Mutt/1.10.1 (2018-07-13) 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: 936587F8BA X-Spamd-Result: default: False [-6.72 / 15.00]; ARC_NA(0.00)[]; FORGED_RECIPIENTS_FORWARDING(0.00)[]; RCVD_COUNT_FIVE(0.00)[6]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; FROM_HAS_DN(0.00)[]; FORWARDED(0.00)[current@mailman.ysv.freebsd.org]; FREEMAIL_FROM(0.00)[gmail.com]; RCPT_COUNT_THREE(0.00)[3]; MIME_GOOD(-0.10)[text/plain]; HAS_XAW(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; R_SPF_SOFTFAIL(0.00)[~all]; SPF_FAIL_FORWARDING(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_IN_DNSWL_MED(-0.20)[5.0.0.0.0.5.0.0.0.0.0.0.0.0.0.0.a.6.0.2.4.5.2.2.0.0.9.1.1.0.0.2.list.dnswl.org : 127.0.9.2]; MX_GOOD(-0.01)[cached: alt3.gmail-smtp-in.l.google.com]; NEURAL_HAM_SHORT(-0.99)[-0.992,0]; IP_SCORE(-3.62)[ip: (-9.87), ipnet: 2001:1900:2254::/48(-4.67), asn: 10310(-3.49), country: US(-0.09)]; RCVD_NO_TLS_LAST(0.10)[]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:10310, ipnet:2001:1900:2254::/48, country:US]; FORGED_RECIPIENTS(0.00)[peter@holm.cc ..,freebsd-current@freebsd.org]; DMARC_POLICY_SOFTFAIL(0.10)[gmail.com : No valid SPF, No valid DKIM,none] X-Rspamd-Server: mx1.freebsd.org X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 28 Nov 2018 17:57:26 -0000 On Wed, Nov 28, 2018 at 10:50:59AM +0100, Peter Holm wrote: > On Wed, Nov 28, 2018 at 01:46:17AM +0200, Konstantin Belousov wrote: > > On Wed, Nov 28, 2018 at 12:54:21AM +0300, Vladimir Kondratyev wrote: > > > Following test case triggers assertion after r340343: > > > > > > > > > #include > > > > > > int > > > main(int argc, char **argv) > > > { > > >         openat(open("/etc", O_RDONLY), "termcap", O_RDONLY | O_BENEATH); > > > } > > > > > > It results in: > > > > > > panic: Assertion (ndp->ni_lcf & NI_LCF_LATCH) != 0 failed at > > > /usr/src/sys/kern/vfs_lookup.c:182 > > > > > > > The following should fix it. Problem was that the topping directory was > > only latched when the initial path was absolute. Since your example > > switched from the relative argument to the absolute symlink, the BENEATH > > tracker rightfully complained that there were no recorded top. > > > > I also added some asserts I used during the debugging. > > > > diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c > > index 78893c4f2bd..7a80775d91d 100644 > > --- a/sys/kern/vfs_lookup.c > > With this patch I got a: > > $ ./beneath.sh > open("a/b") succeeded > stat("a/b > panic: Assertion (ndp->ni_lcf & NI_LCF_LATCH) != 0 failed at ../../../kern/vfs_lookup.c:269 > cpuid = 4 > time = 1543397647 > KDB: stack backtrace: > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe00c71881a0 > vpanic() at vpanic+0x1a3/frame 0xfffffe00c7188200 > panic() at panic+0x43/frame 0xfffffe00c7188260 > namei_handle_root() at namei_handle_root+0xf7/frame 0xfffffe00c71882b0 > namei() at namei+0x617/frame 0xfffffe00c71884f0 > vn_open_cred() at vn_open_cred+0x526/frame 0xfffffe00c7188640 > vn_open() at vn_open+0x4c/frame 0xfffffe00c7188680 > kern_openat() at kern_openat+0x2e9/frame 0xfffffe00c71888e0 > sys_openat() at sys_openat+0x69/frame 0xfffffe00c7188910 > syscallenter() at syscallenter+0x4e3/frame 0xfffffe00c71889f0 > amd64_syscall() at amd64_syscall+0x4d/frame 0xfffffe00c7188ab0 > fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe00c7188ab0 > --- syscall (499, FreeBSD ELF64, sys_openat), rip = 0x8003a215a, rsp = 0x7fffffffe4f8, rbp = 0x7fffffffe5e0 --- > > https://people.freebsd.org/~pho/stress/log/kostik1127.txt Thank you for reporting this. The issue is due to wrong assert, which is valid for later call to namei_handle_root(), but not for the very first call. Below is the updated patch. diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c index 78893c4f2bd..cb69a75ea65 100644 --- a/sys/kern/vfs_lookup.c +++ b/sys/kern/vfs_lookup.c @@ -202,8 +202,10 @@ nameicap_cleanup(struct nameidata *ndp, bool clean_latch) vdrop(nt->dp); uma_zfree(nt_zone, nt); } - if (clean_latch && (ndp->ni_lcf & NI_LCF_LATCH) != 0) + if (clean_latch && (ndp->ni_lcf & NI_LCF_LATCH) != 0) { + ndp->ni_lcf &= ~NI_LCF_LATCH; vrele(ndp->ni_beneath_latch); + } } /* @@ -446,7 +448,7 @@ namei(struct nameidata *ndp) if (error == 0 && dp->v_type != VDIR) error = ENOTDIR; } - if (error == 0 && (ndp->ni_lcf & NI_LCF_BENEATH_ABS) != 0) { + if (error == 0 && (cnp->cn_flags & BENEATH) != 0) { if (ndp->ni_dirfd == AT_FDCWD) { ndp->ni_beneath_latch = fdp->fd_cdir; vrefact(ndp->ni_beneath_latch); @@ -471,6 +473,8 @@ namei(struct nameidata *ndp) vrele(dp); goto out; } + MPASS((ndp->ni_lcf & (NI_LCF_BENEATH_ABS | NI_LCF_LATCH)) != + NI_LCF_BENEATH_ABS); if (((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0 && lookup_cap_dotdot != 0) || ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) == 0 &&