Date: Thu, 21 Aug 2014 13:12:46 +0200 From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <royger@FreeBSD.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Bryan Drewery <bdrewery@FreeBSD.org> Subject: Re: svn commit: r265003 - head/secure/usr.sbin/sshd Message-ID: <53F5D42E.9080908@FreeBSD.org> In-Reply-To: <20140821080541.GE2737@kib.kiev.ua> References: <201404270528.s3R5SEIm054377@svn.freebsd.org> <53F4B381.5010205@FreeBSD.org> <20140820151310.GB2737@kib.kiev.ua> <53F4BC9B.3090405@FreeBSD.org> <53F4BEB1.6070000@FreeBSD.org> <53F4C022.5050804@FreeBSD.org> <20140821080541.GE2737@kib.kiev.ua>
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 21/08/14 10:05, Konstantin Belousov wrote: > On Wed, Aug 20, 2014 at 05:34:58PM +0200, Roger Pau Monn? wrote: >> On 20/08/14 17:28, Bryan Drewery wrote: >>> On 8/20/2014 10:19 AM, Roger Pau Monn? wrote: >>>> On 20/08/14 17:13, Konstantin Belousov wrote: >>>>> On Wed, Aug 20, 2014 at 04:41:05PM +0200, Roger Pau Monn?? >>>>> wrote: >>>>>> On 27/04/14 07:28, Konstantin Belousov wrote: >>>>>>> Author: kib Date: Sun Apr 27 05:28:14 2014 New >>>>>>> Revision: 265003 URL: >>>>>>> http://svnweb.freebsd.org/changeset/base/265003 >>>>>>> >>>>>>> Log: Fix order of libthr and libc in the global dso >>>>>>> list for sshd, by explicitely linking main binary with >>>>>>> -lpthread. Before, libthr appeared in the list due to >>>>>>> dependency of one of the kerberos libs. Due to the >>>>>>> change in ld(1) behaviour of not copying NEEDED entries >>>>>>> from direct dependencies into the link results, the >>>>>>> order becomes reversed. >>>>>>> >>>>>>> The libthr must appear before libc to properly >>>>>>> interpose libc symbols and provide working rtld locks >>>>>>> implementation. The symptom was sshd hanging on rtld >>>>>>> bind lock during nested symbol binding from a signal >>>>>>> handler. >>>>>>> >>>>>>> Approved by: des (openssh maintainer) Sponsored by: >>>>>>> The FreeBSD Foundation MFC after: 1 week >>>>>>> >>>>>>> Modified: head/secure/usr.sbin/sshd/Makefile >>>>>>> >>>>>>> Modified: head/secure/usr.sbin/sshd/Makefile >>>>>>> ============================================================================== >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> - --- head/secure/usr.sbin/sshd/Makefile Sun Apr 27 05:19:01 2014 (r265002) >>>>>>> +++ head/secure/usr.sbin/sshd/Makefile Sun Apr 27 >>>>>>> 05:28:14 2014 (r265003) @@ -57,6 +57,16 @@ CFLAGS+= >>>>>>> -DNONE_CIPHER_ENABLED DPADD+= ${LIBCRYPT} ${LIBCRYPTO} >>>>>>> ${LIBZ} LDADD+= -lcrypt -lcrypto -lz >>>>>>> >>>>>>> +# Fix the order of NEEDED entries for libthr and >>>>>>> libc. The libthr +# needs to interpose libc symbols, >>>>>>> leaving the libthr loading as +# dependency of krb >>>>>>> causes reversed order and broken interposing. Put +# >>>>>>> the threading library last on the linker command line, >>>>>>> just before +# the -lc added by a compiler driver. >>>>>>> +.if ${MK_KERBEROS_SUPPORT} != "no" +DPADD+= >>>>>>> ${LIBPTHREAD} +LDADD+= -lpthread +.endif + .if >>>>>>> defined(LOCALBASE) CFLAGS+= >>>>>>> -DXAUTH_PATH=\"${LOCALBASE}/bin/xauth\" .endif >>>>>> >>>>>> Hello, >>>>>> >>>>>> This change makes the following simple test program fail >>>>>> on the second assert. The problem is that sa_handler == >>>>>> SIG_DFL, and sa_flags == SA_SIGINFO, which according to >>>>>> the sigaction(9) man page is not possible. With this >>>>>> change reverted the test is successful. >>>>> I do not quite follow. >>>>> >>>>> What are the relations between sshd and your test program ? >>>>> Should the test be run somehow specially ? >>>> >>>> No, and frankly that's what I don't understand. I compile >>>> this simple test with `cc -o test test.c`. It fails with >>>> this commit applied, and succeeds without it. >>>> >>>> Roger. >>>> >>> >>> Does it fail if you do not connect with ssh? >> >> Right, it works fine from the serial console, fails when >> executed from ssh. > > I cannot reproduce it locally with your scenario, but the attached > program demonstrates the issue without relying on inheritance and > libthr. > > I think you mis-interpret the man page statement, it only says that > SA_SIGINFO should not be set in new->sa_flags IMO. But I do not see > much sense in the requirement. Note that we do not test flags for > correctness at all. SUSv4 is also silent on the issue. > > If this is important for your case, the following patch prevents > leaking of the flags for ignored of default/action signals. Could > you, please, describe why do you consider this a bug ? IMO, it is an inconsistency to return an invalid old sigaction, I assume that what is returned as the old sigaction should also be valid according to the man page. I realize SUSv4 don't specify such requirement, but it would still be wrong to use SIG_DFL with SA_SIGINFO, since SA_SIGINFO expect the handler to be of the type: void func(int signo, siginfo_t *info, void *context); While SIG_DLF is of type: void func(int signo); There's software out there that (wrongly?) relies on sa_action == SIG_DFL and (sa_flags & SA_SIGINFO) == 0: http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=tools/libxl/libxl_fork.c;h=fa150959adcfa6618342ba1eb0085cbba5f75d0a;hb=HEAD#l338 The sa_flags check done here seems too strong in my opinion, but I still think it's right according to the man page. Roger. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (Darwin) iQEcBAEBAgAGBQJT9dQpAAoJEKXZdqUyumTAgsIH/2xAfa0FjWpCpkvDoNXGVs4K tRDurCFTsaCJZ1xt3aQyPvPALm+qOpBX+i3nTiX4Bg86jbrZRGTag4OeAE6uX3KR TCKaUB6jNUjuNsj5djURIQktbojFj71ID40bM3AXExXN8Gc7e9qqdvo+p82hDFS/ RkwwS9NfTv+yeC/djH+PsApq7OYCrpR0CX1fW6TKwtjdEZpJC4jx5S5TVJoZ2Y0B urlCtrjW6b4oNHqoiDMF4nk48SkuU/JWsTGAbFW6lK+1voyt3y1126uFk5jz144M ZYy4fu6mKEddrwrUFD9Qt9r3shaSLbenBxhc2ZxMT9V4Ws87bVxTSqqzrYsHJ0E= =Qwfa -----END PGP SIGNATURE-----
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