From: Jakub Kicinski <kuba@kernel.org>
To: Sabrina Dubroca <sd@queasysnail.net>
Cc: netdev@vger.kernel.org, Kuniyuki Iwashima <kuniyu@google.com>
Subject: Re: [PATCH net] rtnetlink: fix leak of SRCU struct in rtnl_link_register
Date: Thu, 19 Mar 2026 17:04:09 -0700 [thread overview]
Message-ID: <20260319170409.3b8176d2@kernel.org> (raw)
In-Reply-To: <5ed5489ecdd05c43bd551804f3bd020ae349f3ca.1773849195.git.sd@queasysnail.net>
On Wed, 18 Mar 2026 17:15:15 +0100 Sabrina Dubroca wrote:
> Commit 6b57ff21a310 ("rtnetlink: Protect link_ops by mutex.") swapped
> the EEXIST check with the init_srcu_struct, but didn't add cleanup of
> the SRCU struct we just allocated in case of error.
FWIW AI has spotted a different bug while reviewing this:
As a related question about the srcu lifecycle for these ops structures,
is there a missing synchronize_rcu() in rtnl_link_unregister() that could
cause a use-after-free?
If rtnl_link_ops_get() traverses the link_ops list under rcu_read_lock(),
and rtnl_link_unregister() removes the ops via list_del_rcu() followed
immediately by synchronize_srcu(&ops->srcu) and cleanup_srcu_struct(),
what happens if an rcu reader finds the ops pointer but is preempted
before calling srcu_read_lock()?
Since no srcu readers are technically active yet, synchronize_srcu()
would return immediately, and cleanup_srcu_struct() would free the
per-CPU data. When the preempted reader resumes, wouldn't it execute
srcu_read_lock() on freed data?
Does rtnl_link_unregister() need a synchronize_rcu() after list_del_rcu()
and before destroying the srcu struct to ensure all rcu-side list
traversals have completed?
next prev parent reply other threads:[~2026-03-20 0:04 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-18 16:15 [PATCH net] rtnetlink: fix leak of SRCU struct in rtnl_link_register Sabrina Dubroca
2026-03-19 4:15 ` Kuniyuki Iwashima
2026-03-20 0:04 ` Jakub Kicinski [this message]
2026-03-20 0:05 ` Jakub Kicinski
2026-03-20 7:23 ` Sabrina Dubroca
2026-03-21 0:35 ` Jakub Kicinski
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