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] keys: Fix UAF in key_put()
Date: Tue, 18 Mar 2025 12:36:55 +0100 [thread overview]
Message-ID: <20250318113655.GB14792@redhat.com> (raw)
In-Reply-To: <20250318112245.GA14792@redhat.com>
Either way... I know nothing about security/key, but grep -w key_put
finds
* When it is no longer required, the key should be released using::
void key_put(struct key *key);
Or::
void key_ref_put(key_ref_t key_ref);
These can be called from interrupt context.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
in Documentation/security/keys/core.rst
and since key_user_put() takes key_user_lock with irqs enabled,
key_put()->key_user_put() doesn't look correct...
Oleg.
On 03/18, Oleg Nesterov wrote:
>
> On 03/18, David Howells wrote:
> >
> > --- a/security/keys/key.c
> > +++ b/security/keys/key.c
> > @@ -645,21 +645,30 @@ EXPORT_SYMBOL(key_reject_and_link);
> > */
> > void key_put(struct key *key)
> > {
> > + int quota_flag;
> > + unsigned short len;
> > + struct key_user *user;
> > +
> > if (key) {
> > key_check(key);
> >
> > + quota_flag = test_bit(KEY_FLAG_IN_QUOTA, &key->flags);
> > + len = key->quotalen;
> > + user = key->user;
> > + refcount_inc(&user->usage);
> > if (refcount_dec_and_test(&key->usage)) {
> > unsigned long flags;
> >
> > /* deal with the user's key tracking and quota */
> > - if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
> > - spin_lock_irqsave(&key->user->lock, flags);
> > - key->user->qnkeys--;
> > - key->user->qnbytes -= key->quotalen;
> > - spin_unlock_irqrestore(&key->user->lock, flags);
> > + if (quota_flag) {
> > + spin_lock_irqsave(&user->lock, flags);
> > + user->qnkeys--;
> > + user->qnbytes -= len;
> > + spin_unlock_irqrestore(&user->lock, flags);
> > }
> > schedule_work(&key_gc_work);
> > }
> > + key_user_put(user);
>
> Do we really need the unconditional refcount_inc / key_user_put ?
>
> void key_put(struct key *key)
> {
> if (key) {
> struct key_user *user = NULL;
> unsigned short len;
>
> key_check(key);
>
> if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
> len = key->quotalen;
> user = key->user;
> refcount_inc(&user->usage);
> }
>
> if (refcount_dec_and_test(&key->usage)) {
> unsigned long flags;
>
> /* deal with the user's key tracking and quota */
> if (user) {
> spin_lock_irqsave(&user->lock, flags);
> user->qnkeys--;
> user->qnbytes -= len;
> spin_unlock_irqrestore(&user->lock, flags);
> }
> schedule_work(&key_gc_work);
> }
>
> if (user)
> key_user_put(user);
> }
> }
>
> looks a bit more clear/simple to me...
>
> Oleg.
next prev parent reply other threads:[~2025-03-18 11:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-18 10:14 [PATCH] keys: Fix UAF in key_put() David Howells
2025-03-18 11:22 ` Oleg Nesterov
2025-03-18 11:36 ` Oleg Nesterov [this message]
2025-03-18 13:27 ` David Howells
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