[pmg-devel] applied-series: [PATCH pmg-api 1/2] cluster config: restrict slurp scope to avoid issue parsing network interfaces

[Stoiko Ivanov <s.ivanov@proxmox.com>]

hi,

huge thanks for your persistence and patience while digging into this -
great find!

applied both patches to master and stable-7 (after verifying that it's
affected as well :)


On Mon, 10 Jul 2023 13:36:46 +0200
Fiona Ebner <f.ebner@proxmox.com> wrote:

> As reported in the community forum [0], there is an edge case, where
> querying the network interfaces would not work. In particular, this
> could happen if the hostname cannot be resolved to a non-loopback IP
> (when installing PMG on Debian and forgetting to adapt /etc/hosts for
> example).
> 
> The issue manifested as follows:
> - When setting up the RESTEnvironemnt, the cluster config is read.
> - This reader uses slurp mode by setting the line ending to undef
>   locally.
> - But the subroutine call PVE::Network::get_local_ip() is still part
>   of that local context.
> - When resolving the hostname to a non-loopback IP address failed, the
>   function would read (via the PVE::INotify module) the network
>   interfaces file.
> - As part of that, /proc/net/dev was read all at once, while the
>   interface parsing code expects it line-by-line.
> - The result for reading network interfaces was cached without having
>   detected the interfaces in /proc/net/dev.
> - When a new request came in, the cached result was used (even
>   changing the file to invalidate the cache would only work as long
>   as the cluster config file exists, because otherwise, there would be
>   an attempt to read the cluster config which would read the updated
>   version of the interfaces file while slurping again).
> 
> [0]: https://forum.proxmox.com/threads/129958/
> 
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> ---
>  src/PMG/ClusterConfig.pm | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/src/PMG/ClusterConfig.pm b/src/PMG/ClusterConfig.pm
> index 77b9e60..c52508d 100644
> --- a/src/PMG/ClusterConfig.pm
> +++ b/src/PMG/ClusterConfig.pm
> @@ -170,9 +170,7 @@ sub lock_config {
>  sub read_cluster_conf {
>      my ($filename, $fh) = @_;
>  
> -    local $/ = undef; # slurp mode
> -
> -    my $raw = defined($fh) ? <$fh> : undef;
> +    my $raw = defined($fh) ? do { local $/ = undef; <$fh> } : undef;
>  
>      my $cinfo = PMG::ClusterConfig::Base->parse_config($filename, $raw);
>