From: Oleg Nesterov <oleg@redhat.com>
To: David Howells <dhowells@redhat.com>
Cc: Jarkko Sakkinen <jarkko@kernel.org>, Kees Cook <kees@kernel.org>,
Greg KH <gregkh@linuxfoundation.org>,
Josh Drake <josh@delphoslabs.com>,
Suraj Sonawane <surajsonawane0215@gmail.com>,
keyrings@vger.kernel.org, linux-security-module@vger.kernel.org,
security@kernel.org, stable@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] keys: Fix UAF in key_put()
Date: Wed, 19 Mar 2025 17:30:39 +0100 [thread overview]
Message-ID: <20250319163038.GD26879@redhat.com> (raw)
In-Reply-To: <2874581.1742399866@warthog.procyon.org.uk>
On 03/19, David Howells wrote:
>
> --- a/security/keys/gc.c
> +++ b/security/keys/gc.c
> @@ -218,8 +218,10 @@ static void key_garbage_collector(struct work_struct *work)
> key = rb_entry(cursor, struct key, serial_node);
> cursor = rb_next(cursor);
>
> - if (refcount_read(&key->usage) == 0)
> + if (test_bit(KEY_FLAG_FINAL_PUT, &key->flags)) {
> + smp_mb(); /* Clobber key->user after FINAL_PUT seen. */
> goto found_unreferenced_key;
> + }
>
> if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) {
> if (key->type == key_gc_dead_keytype) {
> diff --git a/security/keys/key.c b/security/keys/key.c
> index 3d7d185019d3..7198cd2ac3a3 100644
> --- a/security/keys/key.c
> +++ b/security/keys/key.c
> @@ -658,6 +658,8 @@ void key_put(struct key *key)
> key->user->qnbytes -= key->quotalen;
> spin_unlock_irqrestore(&key->user->lock, flags);
> }
> + smp_mb(); /* key->user before FINAL_PUT set. */
Can't resist, smp_mb__before_atomic() should equally work,
but this doesn't really matter, please forget.
> + set_bit(KEY_FLAG_FINAL_PUT, &key->flags);
> schedule_work(&key_gc_work);
I believe this patch is correct,
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
next prev parent reply other threads:[~2025-03-19 16:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-19 15:57 [PATCH v2] keys: Fix UAF in key_put() David Howells
2025-03-19 16:30 ` Oleg Nesterov [this message]
2025-03-19 18:11 ` Linus Torvalds
2025-03-19 18:47 ` David Howells
2025-03-20 16:14 ` Jarkko Sakkinen
2025-03-20 16:39 ` David Howells
2025-03-20 17:28 ` Jarkko Sakkinen
2025-03-20 18:46 ` Jarkko Sakkinen
2025-03-20 18:48 ` Jarkko Sakkinen
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