ipc: recv_cmd4 clobbers destination buffer on errors

Handling this should be done at the lowest levels possible;
so away from higher-level lei code.

1 files changed, 4 insertions, 1 deletions

diff --git a/lib/PublicInbox/CmdIPC4.pm b/lib/PublicInbox/CmdIPC4.pm
index 99890244..4bc4c729 100644
--- a/lib/PublicInbox/CmdIPC4.pm
+++ b/lib/PublicInbox/CmdIPC4.pm
@@ -31,7 +31,10 @@ no warnings 'once';
 *recv_cmd4 = sub ($$$) {
         my ($s, undef, $len) = @_; # $_[1] = destination buffer
         my $mh = Socket::MsgHdr->new(buflen => $len, controllen => 256);
-        my $r = Socket::MsgHdr::recvmsg($s, $mh, 0) // return (undef);
+        my $r = Socket::MsgHdr::recvmsg($s, $mh, 0) // do {
+                $_[1] = '';
+                return (undef);
+        };
         $_[1] = $mh->buf;
         return () if $r == 0;
         my (undef, undef, $data) = $mh->cmsghdr;