Observation of a memory leak with commit 314001f0bf92 ("af_unix: Add OOB support")

[Lukas Bulwahn]

Dear Rao and David,


In our syzkaller instance running on linux-next,
https://elisa-builder-00.iol.unh.edu/syzkaller-next/, we have been
observing a memory leak in prepare_creds,
https://elisa-builder-00.iol.unh.edu/syzkaller-next/report?id=1dcac8539d69ad9eb94ab2c8c0d99c11a0b516a3,
for quite some time.

It is reproducible on v5.15-rc1, v5.15, v5.16-rc8 and next-20220104.
So, it is in mainline, was released and has not been fixed in
linux-next yet.

As syzkaller also provides a reproducer, we bisected this memory leak
to be introduced with  commit 314001f0bf92 ("af_unix: Add OOB
support").

We also tested that reverting this commit on torvalds' current tree
made the memory leak with the reproducer go away.

Could you please have a look how your commit introduces this memory
leak? We will gladly support testing your fix in case help is needed.


Best regards,

Lukas