archival: support zstd in rpm and dpkgzstd

1 files changed, 4 insertions, 1 deletions

diff --git a/archival/libarchive/open_transformer.c b/archival/libarchive/open_transformer.c
index 9f41c7b4f..375e7b249 100644
--- a/archival/libarchive/open_transformer.c
+++ b/archival/libarchive/open_transformer.c
@@ -211,11 +211,14 @@ static transformer_state_t *setup_transformer_on_fd(int fd, int die_if_not_compr
         }
 
         if (ENABLE_FEATURE_SEAMLESS_ZSTD && xstate->magic.b16[0] == ZSTD_MAGIC1) {
-                xstate->signature_skipped = 4;
                 xread(fd, &xstate->magic.b16[1], 2);
                 if (xstate->magic.b16[1] == ZSTD_MAGIC2) {
                         xstate->xformer = unpack_zstd_stream;
                         USE_FOR_NOMMU(xstate->xformer_prog = "unzstd";)
+                        // FIXME We execute an external decompressor even on MMU.
+                        // Force a seek back to the signature.
+                        xstate->signature_skipped = 0;
+                        xlseek(xstate->src_fd, -4, SEEK_CUR);
                         goto found_magic;
                 }
         }