Re: [PATCH] devpts: If initialization failed, don't crash when opening /dev/ptmx

Peter Hurley
2015-05-07T23:24:20Z

On 05/07/2015 06:59 PM, Andrew Morton wrote:
> On Wed, 6 May 2015 17:35:47 -0700 Josh Triplett <josh@joshtriplett.org> wrote:
>
>> If devpts failed to initialize, it would store an ERR_PTR in the global
>> devpts_mnt. A subsequent open of /dev/ptmx would call devpts_new_index,
>> which would dereference devpts_mnt and crash.
>>
>> Avoid storing invalid values in devpts_mnt; leave it NULL instead.
>> Make both devpts_new_index and devpts_pty_new fail gracefully with
>> ENODEV in that case, which then becomes the return value to the
>> userspace open call on /dev/ptmx.
>
> It looks like the system is pretty crippled if init_devptr_fs() fails.
> Can the user actually get access to consoles and do useful things in
> this situation? Maybe it would be better to just give up and panic?

A single-user console is definitely reachable without devpts.
>From there, one could fixup to a not-broken kernel.

Regards,
Peter Hurley

PS - But I saw you already added these to -mm