[pmg-devel] [PATCH pmg-api] sa-custom: fix moving config across mountpoints

[Dominik Csapak]

On 10/2/24 19:22, Stoiko Ivanov wrote:
> the custom scores are kept in /var/cache/pmg-scores.cf, until they are
> applied, by moving them to /etc/mail/spamassassin/pmg-scores.cf.
> This currently happens with perl's `rename` function [0], which is a
> wrapper for rename(2). `rename` does not work across filesystem
> boundaries (errors out with EXDEV).
> 
> having `/var` on another filesystem is becoming less common, but
> should probably be supported.
> 
> following the recommendation of [0] switch over to `File::Copy::move`,
> and add some error-checking. File::Copy is shipped with
> perl-modules-5.36, thus it does not introduce a new dependency

well perldoc also says this:

 > If an error occurs during this copy-and-delete process, you may be left with a (possibly partial) 
 > copy of the file under the destination name.

so i'd probably use something like get_contents/set_contents so we can be sure the write
is atomic

otherwise, i agree with thomas that we probably should keep the original in
/etc/mail/spamassassin if it's possible to have a file there that is not parsed
by spamassassin (not sure what logic it uses to read files from there)



> 
> reported in our community-forum:
> https://forum.proxmox.com/threads/.154814/
> 
> tested in a container with a seperate volume for `/var/cache`.
> 
> other occurences of `rename` in the repo should not be affected
> (moving files within the same directory, or e.g. from /etc/pmg/master
> to /etc/pmg).
> 
> [0] https://perldoc.perl.org/functions/rename
> 
> Signed-off-by: Stoiko Ivanov <s.ivanov at proxmox.com>
> ---
>   src/PMG/SACustom.pm | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/src/PMG/SACustom.pm b/src/PMG/SACustom.pm
> index f91ebf2..8b78aff 100644
> --- a/src/PMG/SACustom.pm
> +++ b/src/PMG/SACustom.pm
> @@ -5,6 +5,7 @@ use warnings;
>   
>   use PVE::INotify;
>   use Digest::SHA;
> +use File::Copy qw(move);
>   
>   my $shadow_path = "/var/cache/pmg-scores.cf";
>   my $conf_path = "/etc/mail/spamassassin/pmg-scores.cf";
> @@ -14,7 +15,9 @@ sub get_shadow_path {
>   }
>   
>   sub apply_changes {
> -    rename($shadow_path, $conf_path) if -f $shadow_path;
> +    if (-f $shadow_path) {
> +	move($shadow_path, $conf_path) || die 'Moving custom scores configuration failed!\n';
> +    }
>   }
>   
>   sub calc_digest {