Permissions of alsatplg -o output are hardcoded to S_IRUSR | S_IWUSR (600)

[marc-hb]

From https://github.com/alsa-project/alsa-utils/blob/c8c348e28a258f17e3/topology/topology.c#L172

static int save(const char *output_file, void *buf, size_t size)
{

               fd = open(fname, O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);

When using alsatplg in a build system (e.g.: https://github.com/thesofproject/sof/blob/3e1c160e5053eae/tools/topology/topology1/CMakeLists.txt#L243), all other artefacts follow the process's umask except alsatplg output. This causes subtle and time-consuming errors when trying to share artefacts across different processes.

git blame finds:

commit cbabe7a
Author: Jaroslav Kysela perex@perex.cz
Date: Thu Dec 19 15:36:05 2019 +0100

alsatplg: rewrite to use the new libatopology functions

Before cbabe7a, opening the output file was delegated to library function snd_tplg_build_file(). Not sure what permissions were used then.

Workaround:

alsatplg -c intput.conf -o - > output.tplg

[perexg]

Thank you for your report. It's fixed now in 8e71fba. The problem was in the original code in alsa-lib, too. Several Intel people touched the code and the result ends with this too restrictive permission settings.

• alsa-project/alsa-lib@5b518c915#diff-380e8c90a71ab889257ac12231df110b4a6993eefc83c19368f192419c33ae3cL273
• alsa-project/alsa-lib@37692bb98#diff-380e8c90a71ab889257ac12231df110b4a6993eefc83c19368f192419c33ae3cR273

[marc-hb]

Thanks @perexg for the super quick fix.

Several Intel people touched the code and the result ends with this too restrictive permission settings.

git blame can be cruel :-) Looks like that change was trying to remove spurious exec permissions and went too far. Hard to tell for sure because it's just one line drown in a much bigger commit.