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 D2DCD7F for ; Tue, 7 Jun 2022 18:01:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98F81C385A5; Tue, 7 Jun 2022 18:01:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1654624903; bh=ss5NCjJvt9POin4Vj0SlpF22PHkI6I1R+GC2c+AlgBo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VU4ZLLYui9Jv2UnRaoD2V0f2j69EE/X7PMWozZlZGpBAhr9aKfBMhWqc6pkZNwUgJ uJlEUOWsCutk9RbmIS5i13i4geqOXSJIUxqlofin/xGKovL8pdIjgMExoQu5G1lGXC Bkzk2daY1zRsnGr6k7Gsf/z3kRRKc7HztEUCCzkRgEZrxzUZcildS7tgH9QHcCV2ET 2CEvS9sAGkauHWn8A977ipnbvxgaQV87hGsRxC0AxMkGP4BPl1iKcGqtVk+J79+bcM 0MkXlrjo2D7M/Z159Wt3lEICQhsc8e1yn206b4dD7HDHzVRU/6KnLuvZRoyA862KRj TYS1t9a5PA54Q== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Duoming Zhou , Greg Kroah-Hartman , Sasha Levin , baihaowen@meizu.com, dave@stgolabs.net, len.baker@gmx.com, wangborong@cdjrlc.com, linux-staging@lists.linux.dev Subject: [PATCH AUTOSEL 4.19 05/27] drivers: staging: rtl8192u: Fix deadlock in ieee80211_beacons_stop() Date: Tue, 7 Jun 2022 14:01:09 -0400 Message-Id: <20220607180133.481701-5-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220607180133.481701-1-sashal@kernel.org> References: <20220607180133.481701-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Duoming Zhou [ Upstream commit 806c7b53414934ba2a39449b31fd1a038e500273 ] There is a deadlock in ieee80211_beacons_stop(), which is shown below: (Thread 1) | (Thread 2) | ieee80211_send_beacon() ieee80211_beacons_stop() | mod_timer() spin_lock_irqsave() //(1) | (wait a time) ... | ieee80211_send_beacon_cb() del_timer_sync() | spin_lock_irqsave() //(2) (wait timer to stop) | ... We hold ieee->beacon_lock in position (1) of thread 1 and use del_timer_sync() to wait timer to stop, but timer handler also need ieee->beacon_lock in position (2) of thread 2. As a result, ieee80211_beacons_stop() will block forever. This patch extracts del_timer_sync() from the protection of spin_lock_irqsave(), which could let timer handler to obtain the needed lock. Signed-off-by: Duoming Zhou Link: https://lore.kernel.org/r/20220417135407.109536-1-duoming@zju.edu.cn Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c index 212cc9ccbb96..426966a29d31 100644 --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c @@ -529,9 +529,9 @@ static void ieee80211_beacons_stop(struct ieee80211_device *ieee) spin_lock_irqsave(&ieee->beacon_lock, flags); ieee->beacon_txing = 0; - del_timer_sync(&ieee->beacon_timer); spin_unlock_irqrestore(&ieee->beacon_lock, flags); + del_timer_sync(&ieee->beacon_timer); } void ieee80211_stop_send_beacons(struct ieee80211_device *ieee) -- 2.35.1