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

On Sun, Jan 9, 2022 at 7:49 AM Hillf Danton [off-list ref] wrote:

On Sun, 9 Jan 2022 05:10:48 +0100 Lukas Bulwahn wrote:

quoted

On Fri, Jan 7, 2022 at 6:55 PM Shoaib Rao [off-list ref] wrote:

quoted

Hi Lukas,

I took a look at the patch and I fail to see how prepare_creds() could
be impacted by the patch. The only reference to a cred in the patch is
via maybe_add_creds().

prepare_creds() is called to make a copy of the current creds which will
be later modified. If there is any leak it would be in the caller not
releasing the memory. The patch does not do anything with creds.

If there is any more information that can help identify the issue, I
will be happy to look into it.

Here is more information:

Here are all crash reports:

https://elisa-builder-00.iol.unh.edu/syzkaller-next/crash?id=1dcac8539d69ad9eb94ab2c8c0d99c11a0b516a3

More weid is the failure of Ctrl-f "unix" at [1] except for a bunch of
clone. Can you specify why report at [1] has a direct link to af_unix?

        Hillf

[1] https://elisa-builder-00.iol.unh.edu/syzkaller-next/file?name=crashes%2f1dcac8539d69ad9eb94ab2c8c0d99c11a0b516a3%2freport15

Hillf,

I agree that is really weird. I fear we have some issue with our
syzkaller instance, somehow the database is collecting error logs that
seem to be different from the error logs I observe when manually
running the reproducer. The heuristics of aggregating error messages
is black magic.

Importantly, we have a reproducer, which is clearly related to the
af_unix functionality and we can manually trigger a reasonable error
trace. Ignore all the rest.

Lukas