unbound crashes on bootup

[Eric van Gyzen]

On 02/11/2015 13:06, Jean-Sébastien Pédron wrote:
> On 06.02.2015 14:06, Poul-Henning Kamp wrote:
>> I just updated my -current to r278283, and unbound (still) croaks
>> during bootup:
>
> Hi!
>
> I have a similar problem. Also, unbound crashes each time I start/stop
> OpenVPN. I suppose the problem is the same in both cases.
>
> The crash happens in the config_lookup_uid() in
> contrib/unbound/util/config_file.c. Here's the code:
>
>     struct passwd *pwd;
>     if((pwd = getpwnam(cfg->username)) == NULL)
>         log_err("user '%s' does not exist.", cfg->username);
>     cfg->uid = pwd->pw_uid;

getpwnam() is not thread-safe.  I'm surprised unbound would use it. 
Calling it from multiple threads can cause trouble, although I don't
know off-hand if it could cause this problem.  As an experiment, you
might change it to getpwnam_r() and see it the problem persists.

Otherwise, adding errno to the log message might help.  Be sure to zero
errno before calling getpwnam().

> getpwnam(3) returns NULL: an error message is logged but the function
> doesn't return. Therefore, the program segfaults on "pwd->pw_uid" on the
> next line.
>
> But why did getpwnam(3) return NULL in the first place? It looks for the
> "unbound" user which exists. getpwnam() calls _nsdispatch() which fails.
>
> I have the default nsswitch.conf. I didn't look at the problem more
> deeply yet, but could getpwnam()/_nsdispatch() be unhappy with the
> absence of a working DNS resolver (unbound is being (re)started)?
>