From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1ADD162148; Mon, 8 Apr 2024 13:25:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712582723; cv=none; b=N2aDegoTaiz1PqQaXlbNKR9nRYmlMQv/mrwmHZRmP69Wu/akvJTbGQrFy9cBm5cd6+LhnXtPRL5HSR3MmB+UZPLS30AWlr0OxJ3HY2ilAEIxWn6mjfi8ZoEyWTO6VxnHNqO1QXGXGUR1xvwV+BkrkIPCpIhBzqu89jJDHmzJW5k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712582723; c=relaxed/simple; bh=7IQobet1tRUlGEYgD9heDjVZ+XeNFPysQYLybX28XPE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gf44T7PESIsRvvS7rQdMn6BzYmmXIi3vb7hb0DaQtGiHuGG+8MAEiAdjd7fA9zEdSVe3xPSeV42qf5UC8lZ2zEu3zmJjZ4BeO3LspowMKzW4d/C5nMJQyu6oqTk/EDqjqlyjUKNjGTmCHDH6UqN/dfje5GqLn9gOWYtJfwouTQg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rHNndPLD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="rHNndPLD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 56BC3C433C7; Mon, 8 Apr 2024 13:25:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1712582722; bh=7IQobet1tRUlGEYgD9heDjVZ+XeNFPysQYLybX28XPE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rHNndPLDiyS/JTV6jkgJmpq8lvVl0FuAIiw1PloFCTL/uq3eCSDi6JPyVAs4+3mcy /PlSWso2EBBMqS5F4lDp2Wax52GiwHs3+qmBtpaa5gX3NDfCccu1ny6MfDrYSjSKqx ttgKIU0L63fhEqAIywRZS/0bCcCTnnr1snvQNx8k= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot , Eric Dumazet , Jiri Pirko , Jamal Hadi Salim , Jakub Kicinski Subject: [PATCH 6.8 100/273] net/sched: fix lockdep splat in qdisc_tree_reduce_backlog() Date: Mon, 8 Apr 2024 14:56:15 +0200 Message-ID: <20240408125312.417523553@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240408125309.280181634@linuxfoundation.org> References: <20240408125309.280181634@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet commit 7eb322360b0266481e560d1807ee79e0cef5742b upstream. qdisc_tree_reduce_backlog() is called with the qdisc lock held, not RTNL. We must use qdisc_lookup_rcu() instead of qdisc_lookup() syzbot reported: WARNING: suspicious RCU usage 6.1.74-syzkaller #0 Not tainted ----------------------------- net/sched/sch_api.c:305 suspicious rcu_dereference_protected() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by udevd/1142: #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline] #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline] #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: net_tx_action+0x64a/0x970 net/core/dev.c:5282 #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: net_tx_action+0x754/0x970 net/core/dev.c:5297 #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline] #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline] #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: qdisc_tree_reduce_backlog+0x84/0x580 net/sched/sch_api.c:792 stack backtrace: CPU: 1 PID: 1142 Comm: udevd Not tainted 6.1.74-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024 Call Trace: [] __dump_stack lib/dump_stack.c:88 [inline] [] dump_stack_lvl+0x1b1/0x28f lib/dump_stack.c:106 [] dump_stack+0x15/0x1e lib/dump_stack.c:113 [] lockdep_rcu_suspicious+0x1b9/0x260 kernel/locking/lockdep.c:6592 [] qdisc_lookup+0xac/0x6f0 net/sched/sch_api.c:305 [] qdisc_tree_reduce_backlog+0x243/0x580 net/sched/sch_api.c:811 [] pfifo_tail_enqueue+0x32c/0x4b0 net/sched/sch_fifo.c:51 [] qdisc_enqueue include/net/sch_generic.h:833 [inline] [] netem_dequeue+0xeb3/0x15d0 net/sched/sch_netem.c:723 [] dequeue_skb net/sched/sch_generic.c:292 [inline] [] qdisc_restart net/sched/sch_generic.c:397 [inline] [] __qdisc_run+0x249/0x1e60 net/sched/sch_generic.c:415 [] qdisc_run+0xd6/0x260 include/net/pkt_sched.h:125 [] net_tx_action+0x7c9/0x970 net/core/dev.c:5313 [] __do_softirq+0x2bd/0x9bd kernel/softirq.c:616 [] invoke_softirq kernel/softirq.c:447 [inline] [] __irq_exit_rcu+0xca/0x230 kernel/softirq.c:700 [] irq_exit_rcu+0x9/0x20 kernel/softirq.c:712 [] sysvec_apic_timer_interrupt+0x42/0x90 arch/x86/kernel/apic/apic.c:1107 [] asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:656 Fixes: d636fc5dd692 ("net: sched: add rcu annotations around qdisc->qdisc_sleeping") Reported-by: syzbot Signed-off-by: Eric Dumazet Reviewed-by: Jiri Pirko Acked-by: Jamal Hadi Salim Link: https://lore.kernel.org/r/20240402134133.2352776-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/sched/sch_api.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -809,7 +809,7 @@ void qdisc_tree_reduce_backlog(struct Qd notify = !sch->q.qlen && !WARN_ON_ONCE(!n && !qdisc_is_offloaded); /* TODO: perform the search on a per txq basis */ - sch = qdisc_lookup(qdisc_dev(sch), TC_H_MAJ(parentid)); + sch = qdisc_lookup_rcu(qdisc_dev(sch), TC_H_MAJ(parentid)); if (sch == NULL) { WARN_ON_ONCE(parentid != TC_H_ROOT); break;