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=1792682058; b=YRGmlgUUeuAM5eQl5hctvT+WQF8Czsp+Tpdqqa+PiQSMi4yJpP2aIw7vYNLfX1/LHXGH HPoOPeLTwlXqaj/nqd2a6tXe9+x7YVvQRCqXcCsV4nPMcaWB1QQ+1eIntDvvI4SIVVIaE JfW7laNIFPtEwNQJllDdGAQz+SkEdFzP+aOi8P/Ugk1IrRGLaAg8Y5PNHGNGli8OkbwQr FuRfrIu5G/cqCmAMd7XbUJNMKzPJSxKhytKSXMj47LVKxA9sAeLs4XA5KVlpgiAFWxm8a Y3Q4c2BtOIE6vuJwgByE7I1Hdqg0qZ+CPCIwuovDrBS3LLZIQlRoXjSfjdTOEm0wztw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792682058; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=1liQut5JHI17Yq/A1V7YgqGN1GAoyZTilKH8/Jjrs9g=; b=3K2x4GXqyBbsY+OuQdrHKszVjLmKCnm5brQA3P0n6kPVIW1ej7HIH8OEWy5hOM0dQhC2 OiG18MK8SoKq5VzUmIzRXwunNm3JnNmw5hXsaIvzeSmrNKoGi1opGRLmhrTH0dpHZy5Xi VMd9yYP5VcTnhj5Kooi/Dndv8vP5Ux6coKChgZ5XUrd/Im/VZ7AsODkE1rBypUEUDg/AE KfV7bmlWHiv7OIzvwE07QX+dYbDDEXbXLSeMYDJEfUrydJHNQZyaG4oSLdyzUCrjQIQ2i l5H/zPmFOEUhOt/P8p8gfsmDdxXTPNyoE0g1EEBkbBXkXfQpBUhhMV7psdF3Z9nZvkA== 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=bNS5XQWc; 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 9A502606ACD8 for ; Thu, 22 Oct 2026 15:14:18 +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=bNS5XQWc Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED8381F01829; Thu, 22 Oct 2026 15:14:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792682058; bh=1liQut5JHI17Yq/A1V7YgqGN1GAoyZTilKH8/Jjrs9g=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=bNS5XQWc+hcV50yT1/8fjRQdhFpJWGsQhYM+Io0/9PhrMSud6gUiYBDmdpt9HoUXR WlwjDngcz7lxDFxtENSSYMzqMBDLcuukuwZPeyqyUOo0fF7ROfUlcTpzpUnSqqLFSY tL3HJ7+dWfQ82AIW12h7wRUVdN90MOY2Hu65zR4QPa2Hb+m/tM7K5l/Xx20a8lR8ll 4beBWzPlDU42yl9zg9T14jYYHyzdKRgD5yV0qBi81XtbZ1Zd04r0FwOE4w2OY5BlGk hLCOuf3xFMb6F6TPID0xUqI5PNnwiQC1mef5mOOBZuU19GxUBguoVr2ao8krpr7J79 dRL/iamn9ZHmw== From: Sasha Levin To: stable@vger.kernel.org Cc: Yao Kai , Tejun Heo , Sasha Levin Subject: [PATCH 6.18.y 2/2] workqueue: Fix unbound pool lifetime for pending pwqs Date: Thu, 22 Oct 2026 11:14:15 -0400 Message-ID: <20261022150730.1630145-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261022150730.1630145-1-sashal@kernel.org> References: <2026102148-outpour-epilogue-a40f@gregkh> <20261022150730.1630145-1-sashal@kernel.org> 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 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 b7b09a618d047..8c74f199cd707 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -5185,12 +5185,6 @@ static void pwq_release_workfn(struct kthread_work *work) mutex_unlock(&wq->mutex); } - if (!is_percpu_pool(pool)) { - 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); @@ -5200,6 +5194,12 @@ static void pwq_release_workfn(struct kthread_work *work) raw_spin_unlock_irq(&nna->lock); } + if (!is_percpu_pool(pool)) { + mutex_lock(&wq_pool_mutex); + put_unbound_pool(pool); + mutex_unlock(&wq_pool_mutex); + } + kfree_rcu(pwq, rcu); /* -- 2.53.0