* Re: [syzbot] Monthly lsm report (Apr 2026)
[not found] ` <CAHC9VhS2AaRwAQw1hNcpuGdFSOL7Li9PavKtU7eW-w8eMOFuKA@mail.gmail.com>
@ 2026-05-10 4:02 ` Jarkko Sakkinen
0 siblings, 0 replies; only message in thread
From: Jarkko Sakkinen @ 2026-05-10 4:02 UTC (permalink / raw)
To: Paul Moore, Eric Biggers
Cc: David Howells, linux-kernel, linux-security-module,
syzkaller-bugs, syzbot
On Tue, Apr 14, 2026 at 10:02:13AM -0400, Paul Moore wrote:
> > <2> 68 Yes possible deadlock in keyring_clear (3)
> > https://syzkaller.appspot.com/bug?extid=f55b043dacf43776b50c
>
> Jarkko, David,
>
> Do we have a fix for the keyring_clear() issue, or is it not a real problem?
Sorry for not meeting the timeline I promised.
Anyhow, let's on the issue.
There's really just two alternatives to resolve [1]:
A. balance_pgdat() acquires keyring semaphore before __fs_reclaim_acquire(),
and a non-locking-acquiring aking __keyring_clear() would be called
inside fscrypt_put_master_key().
B. keyring_clear() is deferred and we accept that quota is not
immediately released.
Fixing this from the user process side doing kzalloc() is of course unrealistic,
and unstable fix.
So.. I don't think this is keyring issue per se. This is fscrypt issue
mainly, aand depending on whether A or B are used to sort this out,
possibly also kswapd issue.
Or this is my analysis (which could be wrong of course) after couple
hours looking into it.
[1] https://lore.kernel.org/all/68e54915.a00a0220.298cc0.0480.GAE@google.com/T/
BR, Jarkko
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