Konstantin Belousov
2019-Aug-24 20:41 UTC
ntpd doesn't like ASLR on stable/12 post-r350672
On Sat, Aug 24, 2019 at 10:04:49PM +0200, Trond Endrest?l wrote:> Hi, > > I'm running stable/12 with ASLR enabled in /etc/sysctl.conf: > > kern.elf64.aslr.enable=1 > kern.elf64.aslr.pie_enable=1 > kern.elf32.aslr.enable=1 > kern.elf32.aslr.pie_enable=1 > > After upgrading to anything after r350672, now at r351450, ntpd > refuses to start at boot. > > Aug 24 21:25:42 <ntp.notice> HOSTNAME ntpd[5618]: ntpd 4.2.8p12-a (1): Starting > Aug 24 21:25:43 <kern.info> HOSTNAME kernel: [406] pid 5619 (ntpd), jid 0, uid 123: exited on signal 11 > > Disabling ASLR, kern.elf64.aslr.enable=0, before starting ntpd > manually is a workaround, but this is not viable in the long run.Why ?> > I tried changing command="/usr/sbin/${name}" to > command="/usr/bin/proccontrol -m aslr -s disable /usr/sbin/${name}" in > /etc/rc.d/ntpd, but that didn't go well.If you set kern.elf64.aslr.stack_gap to zero, does it help ?> > Running ntpd through gdb while ASLR was enabled, I narrowed it down to > /usr/src/contrib/ntp/ntpd/ntpd.c:1001 > > ntp_rlimit(RLIMIT_STACK, DFLT_RLIMIT_STACK * 4096, 4096, "4k"); > > which calls /usr/src/contrib/ntp/ntpd/ntp_config.c:5211 and proceeds > to /usr/src/contrib/ntp/ntpd/ntp_config.c:5254 > > if (-1 == getrlimit(RLIMIT_STACK, &rl)) { > > Single stepping from this point gave me: > > ===> > (gdb) s > _thr_rtld_set_flag (mask=1) at /usr/src/lib/libthr/thread/thr_rtld.c:171 > 171 { > (gdb) > 176 return (0); > (gdb) > _thr_rtld_rlock_acquire (lock=0x80180d200) at /usr/src/lib/libthr/thread/thr_rtld.c:115 > 115 { > (gdb) > 120 curthread = _get_curthread(); > (gdb) > _get_curthread () at /usr/src/lib/libthr/arch/amd64/include/pthread_md.h:97 > 97 return (TCB_GET64(tcb_thread)); > (gdb) > _thr_rtld_rlock_acquire (lock=0x80180d200) at /usr/src/lib/libthr/thread/thr_rtld.c:121 > 121 SAVE_ERRNO(); > (gdb) > 124 THR_CRITICAL_ENTER(curthread); > (gdb) > _thr_rwlock_tryrdlock (rwlock=<optimized out>, flags=0) at /usr/src/lib/libthr/thread/thr_umtx.h:192 > 192 (rwlock->rw_flags & URWLOCK_PREFER_READER) != 0) > (gdb) > 191 if ((flags & URWLOCK_PREFER_READER) != 0 || > (gdb) > 197 while (!(state & wrflags)) { > (gdb) > 201 if (atomic_cmpset_acq_32(&rwlock->rw_state, state, state + 1)) > (gdb) > atomic_cmpset_int (dst=<optimized out>, expect=<optimized out>, src=1) at /usr/obj/usr/src/amd64.amd64/tmp/usr/include/machine/atomic.h:220 > 220 ATOMIC_CMPSET(int); > (gdb) > _thr_rwlock_tryrdlock (rwlock=<optimized out>, flags=0) at /usr/src/lib/libthr/thread/thr_umtx.h:201 > 201 if (atomic_cmpset_acq_32(&rwlock->rw_state, state, state + 1)) > (gdb) > _thr_rtld_rlock_acquire (lock=0x80180d200) at /usr/src/lib/libthr/thread/thr_rtld.c:127 > 127 curthread->rdlock_count++; > (gdb) > 128 RESTORE_ERRNO(); > (gdb) > 129 } > (gdb) > _thr_rtld_clr_flag (mask=1) at /usr/src/lib/libthr/thread/thr_rtld.c:181 > 181 { > (gdb) > 182 return (0); > (gdb) > _thr_rtld_lock_release (lock=0x80180d200) at /usr/src/lib/libthr/thread/thr_rtld.c:150 > 150 { > (gdb) > _get_curthread () at /usr/src/lib/libthr/arch/amd64/include/pthread_md.h:97 > 97 return (TCB_GET64(tcb_thread)); > (gdb) > _thr_rtld_lock_release (lock=0x80180d200) at /usr/src/lib/libthr/thread/thr_rtld.c:157 > 157 SAVE_ERRNO(); > (gdb) > 160 state = l->lock.rw_state; > (gdb) > 161 if (_thr_rwlock_unlock(&l->lock) == 0) { > (gdb) > _thr_rwlock_unlock (rwlock=0x80180d200) at /usr/src/lib/libthr/thread/thr_umtx.h:249 > 249 state = rwlock->rw_state; > (gdb) > 250 if ((state & URWLOCK_WRITE_OWNER) != 0) { > (gdb) > 256 if (__predict_false(URWLOCK_READER_COUNT(state) == 0)) > (gdb) > 260 URWLOCK_READER_COUNT(state) == 1)) > { > (gdb) > 259 URWLOCK_READ_WAITERS)) != 0 && > (gdb) > 262 state, state - 1)) > (gdb) > 261 if (atomic_cmpset_rel_32(&rwlock->rw_state, > (gdb) > atomic_cmpset_int (dst=<optimized out>, expect=<optimized out>, src=0) at /usr/obj/usr/src/amd64.amd64/tmp/usr/include/machine/atomic.h:220 > 220 ATOMIC_CMPSET(int); > (gdb) > _thr_rwlock_unlock (rwlock=0x80180d200) at /usr/src/lib/libthr/thread/thr_umtx.h:261 > 261 if (atomic_cmpset_rel_32(&rwlock->rw_state, > (gdb) > _thr_rtld_lock_release (lock=<optimized out>) at /usr/src/lib/libthr/thread/thr_rtld.c:162 > 162 if ((state & URWLOCK_WRITE_OWNER) == 0) > (gdb) > 163 curthread->rdlock_count--; > (gdb) > 164 THR_CRITICAL_LEAVE(curthread); > (gdb) > _thr_ast (curthread=0x80864b000) at /usr/src/lib/libthr/thread/thr_sig.c:271 > 271 if (!THR_IN_CRITICAL(curthread)) { > (gdb) > 272 check_deferred_signal(curthread); > (gdb) > check_deferred_signal (curthread=0x80864b000) at /usr/src/lib/libthr/thread/thr_sig.c:332 > 332 if (__predict_true(curthread->deferred_siginfo.si_signo == 0 || > (gdb) > 351 } > (gdb) > _thr_ast (curthread=0x80864b000) at /usr/src/lib/libthr/thread/thr_sig.c:273 > 273 check_suspend(curthread); > (gdb) > check_suspend (curthread=0x80864b000) at /usr/src/lib/libthr/thread/thr_sig.c:358 > 358 if (__predict_true((curthread->flags & > (gdb) > 401 } > (gdb) > _thr_ast (curthread=0x80864b000) at /usr/src/lib/libthr/thread/thr_sig.c:274 > 274 check_cancel(curthread, NULL); > (gdb) > check_cancel (curthread=0x80864b000, ucp=0x0) at /usr/src/lib/libthr/thread/thr_sig.c:283 > 283 if (__predict_true(!curthread->cancel_pending || > (gdb) > _thr_ast (curthread=<optimized out>) at /usr/src/lib/libthr/thread/thr_sig.c:276 > 276 } > (gdb) > _thr_rtld_lock_release (lock=<optimized out>) at /usr/src/lib/libthr/thread/thr_rtld.c:166 > 166 RESTORE_ERRNO(); > (gdb) > 167 } > (gdb) > getrlimit () at getrlimit.S:3 > 3 RSYSCALL(getrlimit) > (gdb) > ntp_rlimit (rl_what=<optimized out>, rl_value=204800, rl_scale=<optimized out>, rl_sstr=<optimized out>) at /usr/src/contrib/ntp/ntpd/ntp_config.c:5257 > 5257 if (rl_value > rl.rlim_max) { > (gdb) > 5264 rl.rlim_cur = rl_value; > (gdb) > 5265 if (-1 == setrlimit(RLIMIT_STACK, &rl)) { > (gdb) > _thr_rtld_set_flag (mask=1) at /usr/src/lib/libthr/thread/thr_rtld.c:171 > 171 { > (gdb) > 176 return (0); > (gdb) > _thr_rtld_rlock_acquire (lock=0x80180d200) at /usr/src/lib/libthr/thread/thr_rtld.c:115 > 115 { > (gdb) > 120 curthread = _get_curthread(); > (gdb) > _get_curthread () at /usr/src/lib/libthr/arch/amd64/include/pthread_md.h:97 > 97 return (TCB_GET64(tcb_thread)); > (gdb) > _thr_rtld_rlock_acquire (lock=0x80180d200) at /usr/src/lib/libthr/thread/thr_rtld.c:121 > 121 SAVE_ERRNO(); > (gdb) > 124 THR_CRITICAL_ENTER(curthread); > (gdb) > _thr_rwlock_tryrdlock (rwlock=<optimized out>, flags=0) at /usr/src/lib/libthr/thread/thr_umtx.h:192 > 192 (rwlock->rw_flags & URWLOCK_PREFER_READER) != 0) > (gdb) > 191 if ((flags & URWLOCK_PREFER_READER) != 0 || > (gdb) > 197 while (!(state & wrflags)) { > (gdb) > 201 if (atomic_cmpset_acq_32(&rwlock->rw_state, state, state + 1)) > (gdb) > atomic_cmpset_int (dst=<optimized out>, expect=<optimized out>, src=1) at /usr/obj/usr/src/amd64.amd64/tmp/usr/include/machine/atomic.h:220 > 220 ATOMIC_CMPSET(int); > (gdb) > _thr_rwlock_tryrdlock (rwlock=<optimized out>, flags=0) at /usr/src/lib/libthr/thread/thr_umtx.h:201 > 201 if (atomic_cmpset_acq_32(&rwlock->rw_state, state, state + 1)) > (gdb) > _thr_rtld_rlock_acquire (lock=0x80180d200) at /usr/src/lib/libthr/thread/thr_rtld.c:127 > 127 curthread->rdlock_count++; > (gdb) > 128 RESTORE_ERRNO(); > (gdb) > 129 } > (gdb) > _thr_rtld_clr_flag (mask=1) at /usr/src/lib/libthr/thread/thr_rtld.c:181 > 181 { > (gdb) > 182 return (0); > (gdb) > _thr_rtld_lock_release (lock=0x80180d200) at /usr/src/lib/libthr/thread/thr_rtld.c:150 > 150 { > (gdb) > _get_curthread () at /usr/src/lib/libthr/arch/amd64/include/pthread_md.h:97 > 97 return (TCB_GET64(tcb_thread)); > (gdb) > _thr_rtld_lock_release (lock=0x80180d200) at /usr/src/lib/libthr/thread/thr_rtld.c:157 > 157 SAVE_ERRNO(); > (gdb) > 160 state = l->lock.rw_state; > (gdb) > 161 if (_thr_rwlock_unlock(&l->lock) == 0) { > (gdb) > _thr_rwlock_unlock (rwlock=0x80180d200) at /usr/src/lib/libthr/thread/thr_umtx.h:249 > 249 state = rwlock->rw_state; > (gdb) > 250 if ((state & URWLOCK_WRITE_OWNER) != 0) { > (gdb) > 256 if (__predict_false(URWLOCK_READER_COUNT(state) == 0)) > (gdb) > 260 URWLOCK_READER_COUNT(state) == 1)) { > (gdb) > 259 URWLOCK_READ_WAITERS)) != 0 && > (gdb) > 262 state, state - 1)) > (gdb) > 261 if (atomic_cmpset_rel_32(&rwlock->rw_state, > (gdb) > atomic_cmpset_int (dst=<optimized out>, expect=<optimized out>, src=0) at /usr/obj/usr/src/amd64.amd64/tmp/usr/include/machine/atomic.h:220 > 220 ATOMIC_CMPSET(int); > (gdb) > _thr_rwlock_unlock (rwlock=0x80180d200) at /usr/src/lib/libthr/thread/thr_umtx.h:261 > 261 if (atomic_cmpset_rel_32(&rwlock->rw_state, > (gdb) > _thr_rtld_lock_release (lock=<optimized out>) at /usr/src/lib/libthr/thread/thr_rtld.c:162 > 162 if ((state & URWLOCK_WRITE_OWNER) == 0) > (gdb) > 163 curthread->rdlock_count--; > (gdb) > 164 THR_CRITICAL_LEAVE(curthread); > (gdb) > _thr_ast (curthread=0x80864b000) at /usr/src/lib/libthr/thread/thr_sig.c:271 > 271 if (!THR_IN_CRITICAL(curthread)) { > (gdb) > 272 check_deferred_signal(curthread); > (gdb) > check_deferred_signal (curthread=0x80864b000) at /usr/src/lib/libthr/thread/thr_sig.c:332 > 332 if > (__predict_true(curthread->deferred_siginfo.si_signo == 0 || > (gdb) > 351 } > (gdb) > _thr_ast (curthread=0x80864b000) at /usr/src/lib/libthr/thread/thr_sig.c:273 > 273 check_suspend(curthread); > (gdb) > check_suspend (curthread=0x80864b000) at /usr/src/lib/libthr/thread/thr_sig.c:358 > 358 if (__predict_true((curthread->flags & > (gdb) > 401 } > (gdb) > _thr_ast (curthread=0x80864b000) at /usr/src/lib/libthr/thread/thr_sig.c:274 > 274 check_cancel(curthread, NULL); > (gdb) > check_cancel (curthread=0x80864b000, ucp=0x0) at /usr/src/lib/libthr/thread/thr_sig.c:283 > 283 if (__predict_true(!curthread->cancel_pending || > (gdb) > _thr_ast (curthread=<optimized out>) at /usr/src/lib/libthr/thread/thr_sig.c:276 > 276 } > (gdb) > _thr_rtld_lock_release (lock=<optimized out>) at /usr/src/lib/libthr/thread/thr_rtld.c:166 > 166 RESTORE_ERRNO(); > (gdb) > 167 } > (gdb) > setrlimit () at setrlimit.S:3 > 3 RSYSCALL(setrlimit) > (gdb) > > Program received signal SIGSEGV, Segmentation fault. > setrlimit () at setrlimit.S:3 > 3 RSYSCALL(setrlimit) > (gdb) > > Program terminated with signal SIGSEGV, Segmentation fault. > The program no longer exists. > (gdb) q > > ===> > I'm sorry for the long post. Is there anything (else) I can do to > further narrow it down? > > -- > Trond. > _______________________________________________ > freebsd-stable at freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe at freebsd.org"
On Sat, 24 Aug 2019 23:41+0300, Konstantin Belousov wrote:> On Sat, Aug 24, 2019 at 10:04:49PM +0200, Trond Endrest?l wrote: > > > Disabling ASLR, kern.elf64.aslr.enable=0, before starting ntpd > > manually is a workaround, but this is not viable in the long run. > > Why ?I like to keep ALSR enabled in the hope that it actually achieves something. You are right, I can disable it completely.> > I tried changing command="/usr/sbin/${name}" to > > command="/usr/bin/proccontrol -m aslr -s disable /usr/sbin/${name}" in > > /etc/rc.d/ntpd, but that didn't go well. > > If you set kern.elf64.aslr.stack_gap to zero, does it help ?That helped. Thank you again. -- Trond.