[mosh-users] mosh-server fails to start on grsecurity kernel

[John Hood]

Try running 

strace -ffo trace mosh --local 127.0.0.1

on that server after enabling coredumps. That's not exactly the same as normal execution, since it doesn't use ssh, but it's useful for issues like this one.

regards,

  --jh

> On Jun 7, 2016, at 12:56 AM, Deven Lahoti <deywos at mit.edu> wrote:
> 
> Neither strace nor gdb will give me a backtrace, since they both lose track of it when it forks, but the failure happens after forking. For some reason, systemd says that coredumps are disabled for the process, so I can't get one of those either.
> 
>> On Jun 7, 2016 00:31, "Alex Chernyakhovsky" <achernya at mit.edu> wrote:
>> Unfortunately, that's not much to go on. Could you grab the core file
>> and get a backtrace? I'm assuming some syscall (probably malloc?)
>> failed.
>> 
>> Sincerely,
>> -Alex
>> 
>> On Tue, Jun 7, 2016 at 12:18 AM, Deven Lahoti <deywos at mit.edu> wrote:
>> > I don't think that's the problem, since it's now giving me:
>> > mosh-server[21489]: segfault at 0 ip           (null) sp 00007fffffffcbd8
>> > error 14 in mosh-server[555555554000+60000]
>> >
>> > On Mon, Jun 6, 2016 at 11:42 PM, Alex Chernyakhovsky <achernya at mit.edu>
>> > wrote:
>> >>
>> >> I think the offending line is
>> >>
>> >> Jun 06 22:32:19 <hostname> kernel: PAX: From 18.X.X.X: execution
>> >> attempt in: (null), 00000000-00000000 00000000
>> >> Jun 06 22:32:19 <hostname> kernel: PAX: terminating task:
>> >> /usr/bin/mosh-server(mosh-server):12505, uid/euid: XXXX/XXXX, PC:
>> >>       (nil), SP: 000003844385a508
>> >>
>> >> mosh-server needs to fork and exec to start subprocesses, and your
>> >> kernel/configuration doesn't consider mosh-server to be in the
>> >> whitelist.
>> >>
>> >> Sincerely,
>> >> -Alex
>> >>
>> >>
>> >> On Mon, Jun 6, 2016 at 11:30 PM, Deven Lahoti <deywos at mit.edu> wrote:
>> >> > Hi, when trying to connect to my machine running Gentoo Hardened on
>> >> > kernel
>> >> > 4.4.8, mosh-server fails to start. Here are the logs (modified to remove
>> >> > personal info) [http://web.mit.edu/deywos/www/mosh.log]. I'm not really
>> >> > sure
>> >> > what the problem is, and I don't know much about how mosh works, so I
>> >> > was
>> >> > hoping someone here could help me out.
>> >> >
>> >> > Thanks,
>> >> > Deven
>> >> >
>> >> > _______________________________________________
>> >> > mosh-users mailing list
>> >> > mosh-users at mit.edu
>> >> > http://mailman.mit.edu/mailman/listinfo/mosh-users
>> >> >
>> >
>> >
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