Re: nsswitch: do not reload if "/" changes

[Florian Weimer via Libc-alpha <libc-alpha@sourceware.org>]

* DJ Delorie via Libc-alpha:

> diff --git a/nss/nss_database.c b/nss/nss_database.c
> index e719ec0865..580ea7b963 100644
> --- a/nss/nss_database.c
> +++ b/nss/nss_database.c
> @@ -33,6 +33,11 @@ struct nss_database_state
>  {
>    struct nss_database_data data;
>    __libc_lock_define (, lock);
> +  /* If "/" changes, we switched into a container and do NOT want to
> +     reload anything.  This data must be persistent across
> +     reloads.  */
> +  ino64_t root_ino;
> +  ino64_t root_dev;
>  };

dev_t for root_dev?

> @@ -53,6 +58,8 @@ global_state_allocate (void *closure)
>        memset (result->data.services, 0, sizeof (result->data.services));
>        result->data.initialized = true;
>        result->data.reload_disabled = false;
> +      result->root_ino = 0;
> +      result->root_dev = 0;
>        __libc_lock_init (result->lock);
>      }

Perhaps you can match the declaration order in the initialization?

> diff --git a/nss/nss_database.h b/nss/nss_database.h
> index 1f827e6def..f94c629174 100644
> --- a/nss/nss_database.h
> +++ b/nss/nss_database.h
> @@ -75,6 +75,10 @@ struct nss_database_data
>    nss_action_list services[NSS_DATABASE_COUNT];
>    int reload_disabled;          /* Actually bool; int for atomic access.  */
>    bool initialized;
> +  /* If "/" changes, we switched into a container and do NOT want to
> +     reload anything.  */
> +  ino64_t root_ino;
> +  ino64_t root_dev;
>  };
>  
>  /* Called by fork in the parent process, before forking.  */

This does not seem to be needed?

Rest looks good.

I have one remaining question: Should we load service modules after /
has changed?  Disabling reloading brings us back to the old behavior in
terms of exposure to untrusted /, but maybe we can do even better and
stop loading service modules altogether?  Assuming that this change is
compatible with init systems.

Thanks,
Florian
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