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 6C1C81C31 for ; Wed, 23 Nov 2022 09:55:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0454C433D7; Wed, 23 Nov 2022 09:55:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1669197355; bh=8HKXCGGVFpmxdo+NKF8LQteVHYmNXwRyQa8UNM5udUs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yp++RwPcixDKF4iYoqbf8Pz6Btd2jl6dsgDoHNcX0EITHWS4+olWwkYTzQ3uTmqQf NORXxmmAD7kLdEvDfWK42Hhb4Z4oU6OAsRgJoZRk/+0gk8JgyNOLIptpCq1q9126IE de+9oDzD+UcE8pewL7xNBJwQIsJup78jqSz+1fBo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Duoming Zhou Subject: [PATCH 6.0 240/314] usb: chipidea: fix deadlock in ci_otg_del_timer Date: Wed, 23 Nov 2022 09:51:25 +0100 Message-Id: <20221123084636.350193169@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123084625.457073469@linuxfoundation.org> References: <20221123084625.457073469@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Duoming Zhou commit 7a58b8d6021426b796eebfae80983374d9a80a75 upstream. There is a deadlock in ci_otg_del_timer(), the process is shown below: (thread 1) | (thread 2) ci_otg_del_timer() | ci_otg_hrtimer_func() ... | spin_lock_irqsave() //(1) | ... ... | hrtimer_cancel() | spin_lock_irqsave() //(2) (block forever) We hold ci->lock in position (1) and use hrtimer_cancel() to wait ci_otg_hrtimer_func() to stop, but ci_otg_hrtimer_func() also need ci->lock in position (2). As a result, the hrtimer_cancel() in ci_otg_del_timer() will be blocked forever. This patch extracts hrtimer_cancel() from the protection of spin_lock_irqsave() in order that the ci_otg_hrtimer_func() could obtain the ci->lock. What`s more, there will be no race happen. Because the "next_timer" is always under the protection of spin_lock_irqsave() and we only check whether "next_timer" equals to NUM_OTG_FSM_TIMERS in the following code. Fixes: 3a316ec4c91c ("usb: chipidea: use hrtimer for otg fsm timers") Cc: stable Signed-off-by: Duoming Zhou Link: https://lore.kernel.org/r/20220918033312.94348-1-duoming@zju.edu.cn Signed-off-by: Greg Kroah-Hartman --- drivers/usb/chipidea/otg_fsm.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/usb/chipidea/otg_fsm.c +++ b/drivers/usb/chipidea/otg_fsm.c @@ -256,8 +256,10 @@ static void ci_otg_del_timer(struct ci_h ci->enabled_otg_timer_bits &= ~(1 << t); if (ci->next_otg_timer == t) { if (ci->enabled_otg_timer_bits == 0) { + spin_unlock_irqrestore(&ci->lock, flags); /* No enabled timers after delete it */ hrtimer_cancel(&ci->otg_fsm_hrtimer); + spin_lock_irqsave(&ci->lock, flags); ci->next_otg_timer = NUM_OTG_FSM_TIMERS; } else { /* Find the next timer */