Konstantin Belousov
2019-Aug-24 22:28 UTC
ntpd doesn't like ASLR on stable/12 post-r350672
On Sun, Aug 25, 2019 at 12:19:43AM +0200, Trond Endrest?l wrote:> On Sat, 24 Aug 2019 23:41+0300, Konstantin Belousov wrote: > > > 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.Can you verify is ntpd sets new rlimit(RLIMIT_STACK) for the main thread, and if yes, what this new limit is ? aslr.stack_gap is the percentage for the gap on that stack, and since default size of the main stack limit is quite large 512M, even 3% (default gap upper limit) are whole 15M. If the new limit is less than 15M, there is a likely probability that only the gap is left after the rlimit(2) call, leaving no space for the program frames. At least this looks like a nice theory.
On Sun, 25 Aug 2019 01:28+0300, Konstantin Belousov wrote:> On Sun, Aug 25, 2019 at 12:19:43AM +0200, Trond Endrest?l wrote: > > On Sat, 24 Aug 2019 23:41+0300, Konstantin Belousov wrote: > > > > 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. > > Can you verify is ntpd sets new rlimit(RLIMIT_STACK) for the main thread, > and if yes, what this new limit is ?(gdb) 5265 if (-1 == setrlimit(RLIMIT_STACK, &rl)) { (gdb) print rl $1 = {rlim_cur = 204800, rlim_max = 536870912}> aslr.stack_gap is the percentage for the gap on that stack, and since > default size of the main stack limit is quite large 512M, even 3% > (default gap upper limit) are whole 15M. If the new limit is less than > 15M, there is a likely probability that only the gap is left after the > rlimit(2) call, leaving no space for the program frames. > > At least this looks like a nice theory.-- Trond.