From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792679661; b=HvQ8J8jiBiONqZsWB2B2grhrrZHHn9piQUwMc9Bwle2ZX+BmgrUkiIeg2mhCOMT0iCFx LBTKyHvfqTTKtj8UP93kPNU/BNkEtkOmjotxZHkGfazLJa4RTmyNov5rqC4qPGzGqRHbn wcS/B0OsShe+5l4u0KM0jauUebt+xml2NbdRkJZYAV/3PCqQKpJOWY9NMIUHBWnx7KkZh Wx4nLnkeKfFbVBjpwJ+U2VyqI5kvwb2kz3dltWRiRQLhLogVb9zSp6vKULftN/LrNcszL UnkKRUyp3oamHkEyjl/MfLtyjsroMsUtOuvz6KodG4DyLn4TQvBKPdWVdI5z646SN7A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792679661; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=jMXA9NISD59AwsiBya0bfW7orjFqWJakaxCvo0rmSAM=; b=A91wBG72eOQAnQZV5hqUjxlrmb/issLh/BnXg/0Fq8BLv26jiUGrnfhDVxyWb4wZTgkV eb4E1oMLzsu301FubrcLxbg71cAXtl3fQE6WSJ/CBNJsR0l8PcCdhvrJXwZrH9sSsrzG6 zui9LFzcTzag/WDCMQv3/vEo8tpZM9Hw7FY+8/w5pe9cRp3xe3xL8JkLHp34JfUTE3PdJ RrV1mFOhklZW+oSpequilvKHA3fGDdORQFdObQsE9U2EBrYvV7Mcoq81ocNyoedKnwWmD 5mRydIm5LAw7iJQZK0lUp2HqNnOETF25rFnunycvlQC2URfgtiG71ICE4502zBBUj1g== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=VxqtQPvn; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E6112606A31D for ; Thu, 22 Oct 2026 14:34:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=VxqtQPvn Received: by smtp.kernel.org (Postfix) with ESMTPSA id 112661F000C1; Thu, 22 Oct 2026 14:34:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792679660; bh=jMXA9NISD59AwsiBya0bfW7orjFqWJakaxCvo0rmSAM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=VxqtQPvnjKoowdM53EJlSYe9vUjkOvPfl8XL8It6rBYGOV5AdS/vOhz4GKLyRIXw5 xbTUhV97fdRFAyO+DVXzQyqvdqCeIUyyn1eSw+TvbWq6/D+0slrWmVP094Y1+l5r5l 2NA6MVSRKcfI/xfsnAjvc5Uxw5ggSWQNQAHVC0+xEFvM7GIPFZCBHqcyezFidTeUGS f1DROdGEj5xNGfYHzradmMan/BF14Ob5sMye82CyPpoHoe+1B3GdOddQ4d2dSW8YzH xoCTz+JbW2qTsh4QFGdOhMf/JdRcYH3RJ0kjNglYMT3QNO8BjjDgFWp+WK0xH2Eh4M d4G3UMms8gkyQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Yao Kai , Tejun Heo , Sasha Levin Subject: [PATCH 7.2.y] workqueue: Fix unbound pool lifetime for pending pwqs Date: Thu, 22 Oct 2026 10:34:18 -0400 Message-ID: <20261022143409.1606096-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026102147-clatter-yen-51fa@gregkh> References: <2026102147-clatter-yen-51fa@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Yao Kai [ Upstream commit cf9c8aaea0d47410df8708bec195889f3a85cd3c ] KASAN reports a use-after-free of an unbound worker_pool in node_activate_pending_pwq(): BUG: KASAN: slab-use-after-free in _raw_spin_trylock+0x6d/0x120 Read of size 4 at addr ffff8880089ce000 by task kworker/u22:0/318 CPU: 1 UID: 0 PID: 318 Comm: kworker/u22:0 Not tainted 7.2.0 #1 PREEMPT(lazy) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Workqueue: 0x0 (flush-8:0) Call Trace: dump_stack_lvl+0x53/0x70 print_report+0xce/0x610 kasan_report+0xce/0x100 _raw_spin_trylock+0x6d/0x120 pwq_dec_nr_in_flight+0x4b4/0xcb0 process_one_work+0x921/0x11a0 worker_thread+0x4d0/0xd20 kthread+0x2de/0x3c0 ret_from_fork+0x3aa/0x620 ret_from_fork_asm+0x1a/0x30 Allocated by task 311: alloc_pwq+0x439/0xca0 apply_wqattrs_prepare+0x75e/0xd10 apply_workqueue_attrs_locked+0x44/0xa0 wq_nice_store+0x350/0x450 Freed by task 0: kfree+0x127/0x3b0 rcu_core+0x523/0x1780 handle_softirqs+0x1b3/0x610 Last potentially related work creation: put_unbound_pool+0x3f3/0x7d0 pwq_release_workfn+0x494/0x8e0 kthread_worker_fn+0x1ff/0x790 Canceling the last inactive work skips pwq_dec_nr_active(), so an empty pwq can remain on pending_pwqs when its refcnt reaches zero. pwq_release_workfn() currently puts the pool before removing that pwq. If this drops the last pool reference, the pool can be RCU-freed while the pwq remains reachable, and node_activate_pending_pwq() may trylock the freed pool->lock. Remove the pwq from pending_pwqs before putting the pool. Fixes: 5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues") Cc: stable@vger.kernel.org Signed-off-by: Yao Kai Signed-off-by: Tejun Heo [ sashal: Replaced `!is_percpu_pool(pool)` with the existing `wq->flags & WQ_UNBOUND` check because the helper is unavailable. ] Signed-off-by: Sasha Levin --- kernel/workqueue.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 9b0bdb5df4465..a65618b6d150d 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -5229,12 +5229,6 @@ static void pwq_release_workfn(struct kthread_work *work) mutex_unlock(&wq->mutex); } - if (wq->flags & WQ_UNBOUND) { - mutex_lock(&wq_pool_mutex); - put_unbound_pool(pool); - mutex_unlock(&wq_pool_mutex); - } - if (!list_empty(&pwq->pending_node)) { struct wq_node_nr_active *nna = wq_node_nr_active(pwq->wq, pwq->pool->node); @@ -5244,6 +5238,12 @@ static void pwq_release_workfn(struct kthread_work *work) raw_spin_unlock_irq(&nna->lock); } + if (wq->flags & WQ_UNBOUND) { + mutex_lock(&wq_pool_mutex); + put_unbound_pool(pool); + mutex_unlock(&wq_pool_mutex); + } + kfree_rcu(pwq, rcu); /* -- 2.53.0