svn commit: r265003 - head/secure/usr.sbin/sshd
Konstantin Belousov
kostikbel at gmail.com
Thu Aug 21 12:32:53 UTC 2014
On Thu, Aug 21, 2014 at 01:12:46PM +0200, Roger Pau Monn? wrote:
> -----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.
Apparently, the original problem requires /bin/sh as the login shell to
reproduce, while I used zsh on the test box.
Below is the patch which fixes reset of flags both for sigaction(2)
and execve(2).
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 561ea0a..4077ec9 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -621,6 +621,15 @@ sig_ffs(sigset_t *set)
return (0);
}
+static bool
+sigact_flag_test(struct sigaction *act, int flag)
+{
+
+ return ((act->sa_flags & flag) != 0 &&
+ (__sighandler_t *)act->sa_sigaction != SIG_IGN &&
+ (__sighandler_t *)act->sa_sigaction != SIG_DFL);
+}
+
/*
* kern_sigaction
* sigaction
@@ -679,7 +688,7 @@ kern_sigaction(td, sig, act, oact, flags)
ps->ps_catchmask[_SIG_IDX(sig)] = act->sa_mask;
SIG_CANTMASK(ps->ps_catchmask[_SIG_IDX(sig)]);
- if (act->sa_flags & SA_SIGINFO) {
+ if (sigact_flag_test(act, SA_SIGINFO)) {
ps->ps_sigact[_SIG_IDX(sig)] =
(__sighandler_t *)act->sa_sigaction;
SIGADDSET(ps->ps_siginfo, sig);
@@ -687,19 +696,19 @@ kern_sigaction(td, sig, act, oact, flags)
ps->ps_sigact[_SIG_IDX(sig)] = act->sa_handler;
SIGDELSET(ps->ps_siginfo, sig);
}
- if (!(act->sa_flags & SA_RESTART))
+ if (sigact_flag_test(act, SA_RESTART))
SIGADDSET(ps->ps_sigintr, sig);
else
SIGDELSET(ps->ps_sigintr, sig);
- if (act->sa_flags & SA_ONSTACK)
+ if (sigact_flag_test(act, SA_ONSTACK))
SIGADDSET(ps->ps_sigonstack, sig);
else
SIGDELSET(ps->ps_sigonstack, sig);
- if (act->sa_flags & SA_RESETHAND)
+ if (sigact_flag_test(act, SA_RESETHAND))
SIGADDSET(ps->ps_sigreset, sig);
else
SIGDELSET(ps->ps_sigreset, sig);
- if (act->sa_flags & SA_NODEFER)
+ if (sigact_flag_test(act, SA_NODEFER))
SIGADDSET(ps->ps_signodefer, sig);
else
SIGDELSET(ps->ps_signodefer, sig);
@@ -935,6 +944,11 @@ execsigs(struct proc *p)
sigqueue_delete_proc(p, sig);
}
ps->ps_sigact[_SIG_IDX(sig)] = SIG_DFL;
+ SIGDELSET(ps->ps_siginfo, sig);
+ SIGDELSET(ps->ps_sigintr, sig);
+ SIGDELSET(ps->ps_sigonstack, sig);
+ SIGDELSET(ps->ps_sigreset, sig);
+ SIGDELSET(ps->ps_signodefer, sig);
}
/*
* Reset stack state to the user stack.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 819 bytes
Desc: not available
URL: <http://lists.freebsd.org/pipermail/svn-src-all/attachments/20140821/9ed6c8fb/attachment.sig>
More information about the svn-src-all
mailing list