[PATCH v2] erofs-utils: tar: support archives without end-of-archive entry

[Gao Xiang]

On 2025/10/2 01:13, Ivan Mikheykin wrote:
> Tar standard https://www.gnu.org/software/tar/manual/html_node/Standard.html
> says that archive "terminated by an end-of-archive entry,
> which consists of two 512 blocks of zero bytes".
> 
> Is also says:
> 
> "A reasonable system should write such end-of-file marker at the end
> of an archive, but must not assume that such a block exists when
> reading an archive. In particular, GNU tar does not treat missing
> end-of-file marker as an error and silently ignores the fact."
> 
> It is rare for erofs to encounter such problem, as images are mostly
> built with docker or buildah. But if you create image using tar library
> in Golang directly uploading layers to registry, you'll get tar layers
> without end-of-archive block. Running containers with such images will
> trigger this error during extraction:
> 
> mkfs.erofs --tar=f --aufs --quiet -Enoinline_data test.erofs test-no-end.tar
> <E> erofs: failed to read header block @ 42496
> <E> erofs: 	Could not format the device : [Error 5] Input/output error
> 
> This patch fixes the problem by assuming that eof is equal to the end-of-archive.
> 
> Reproducible tar without end-of-archive (base64-encoded gzipped blob):
> H4sICKVi2mgAA3Rlc3QtMTAtMi1ibG9ja3MudGFyAAtzDQr29PdjoCUwAAIzExMwbW5mCqYN
> jQzANBgYGTEYmhqYmpqamRoaGTMYGBqaGJkyKBjQ1FVQUFpcklikoMCQkpmYll9ahFNdYkpu
> Zh49HERfYKhnoWdowGVkYGSqa2Cua2jKNdAuGgX0BADwFwqsAAQAAA==
> 
> Also, add warning about non-conformant tar layers:
> 
> mkfs.erofs --tar=f --aufs -Enoinline_data test.erofs test-no-end.tar
> mkfs.erofs 1.8.10-g0a2bc574-dirty
> <W> erofs: unexpected end of file @ 1024 (may be non-standard tar without end of archive zeros)
> Build completed.
> ...
> 
> Signed-off-by: Ivan Mikheykin <ivan.mikheykin at flant.com>

Thanks, will apply.

Thanks,
Gao Xiang