From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from azure-sdnproxy.icoremail.net (azure-sdnproxy.icoremail.net [20.231.56.155]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C26A1185F27; Mon, 25 Mar 2024 03:40:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=20.231.56.155 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711338023; cv=none; b=rPxJOMs0swrdxtOBfJ6YmCo8Eif14NUT8je4waZ9DfaViMJQgB+aF3LPxVofx8ldyN1/FeRcwJmmR5vFzKULvdGRmwGQ76jQkBvz8s5WSlZ+mTePj+Hm3Rea82CLY6yTG7SxdZier5oDvL71hY17J4+9+hH6bsL0QmT5pILhvyA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711338023; c=relaxed/simple; bh=cm6ZnN81c2x49XQx/b2mFqGyUdAzRwWF8NYiQkUhL2c=; h=From:To:Cc:Subject:Date:Message-Id; b=DgxNrLw6RcfuntButEW9Gfzx0aZqQDJbuEMz0j/dJmMhiyKGppcasHlkeD9tmiekx7SWtve8HttJHUsUkcXksv2lqy754Vhx+w8YjxFy5tFM26iSTSGdoqawlaRoGILdRCkfmo9psbRHc7ImYdppvKdwaw32AMILiVAhcv+h4Ro= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=zju.edu.cn; spf=pass smtp.mailfrom=zju.edu.cn; arc=none smtp.client-ip=20.231.56.155 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=zju.edu.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zju.edu.cn Received: from ubuntu.localdomain (unknown [218.12.19.154]) by mail-app4 (Coremail) with SMTP id cS_KCgBXeb0C8gBmkGxFAQ--.46008S2; Mon, 25 Mar 2024 11:39:56 +0800 (CST) From: Duoming Zhou To: linux-sound@vger.kernel.org Cc: linux-kernel@vger.kernel.org, tiwai@suse.com, perex@perex.cz, Duoming Zhou Subject: [PATCH] ALSA: sh: aica: reorder cleanup operations to avoid UAF bug Date: Mon, 25 Mar 2024 11:39:46 +0800 Message-Id: <20240325033946.47052-1-duoming@zju.edu.cn> X-Mailer: git-send-email 2.17.1 X-CM-TRANSID:cS_KCgBXeb0C8gBmkGxFAQ--.46008S2 X-Coremail-Antispam: 1UD129KBjvJXoW7Cr4UZw1kZFWxuFWDCrykXwb_yoW8Ar1fpF Z8WF93KFn7KFyvkFWUZrn2gryxGw1fta1Dtw45J3yjvFs3Xr1Fka45K3ySgFW3trZ5u39r tw45Xw1avr90va7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkl14x267AKxVWUJVW8JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26F4U JVW0owA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oV Cq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0 I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r 4UM4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwCY1x0262kKe7AKxVWU AVWUtwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14 v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_JF0_Jw1lIxkG c2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI 0_Jr0_Gr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4U MIIF0xvEx4A2jsIEc7CjxVAFwI0_Jr0_GrUvcSsGvfC2KfnxnUUI43ZEXa7VUjuHq7UUUU U== X-CM-SenderInfo: qssqjiasttq6lmxovvfxof0/1tbiAwMJAWX+3hkBYwBgsW Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The dreamcastcard->timer could schedule the spu_dma_work and the spu_dma_work could also arm the dreamcastcard->timer. When the Yamaha AICA card is closing, the dreamcastcard->channel will be deallocated. But it could still be dereferenced in the worker thread. The reason is that del_timer() will return directly regardless of whether the timer handler is running or not and the worker could be rescheduled in the timer handler. As a result, the UAF bug will happen. The racy situation is shown below: (Thread 1) | (Thread 2) snd_aicapcm_pcm_close() | ... | run_spu_dma() //worker | mod_timer() flush_work() | del_timer() | aica_period_elapsed() //timer kfree(dreamcastcard->channel) | schedule_work() | run_spu_dma() //worker ... | dreamcastcard->channel-> //USE In order to mitigate this bug, use timer_shutdown_sync() to shutdown the timer and then use flush_work() to cancel the worker. Fixes: 198de43d758c ("[ALSA] Add ALSA support for the SEGA Dreamcast PCM device") Signed-off-by: Duoming Zhou --- sound/sh/aica.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sound/sh/aica.c b/sound/sh/aica.c index 320ac792c7f..bc68a3903f2 100644 --- a/sound/sh/aica.c +++ b/sound/sh/aica.c @@ -354,8 +354,8 @@ static int snd_aicapcm_pcm_close(struct snd_pcm_substream *substream) { struct snd_card_aica *dreamcastcard = substream->pcm->private_data; + timer_shutdown_sync(&dreamcastcard->timer); flush_work(&(dreamcastcard->spu_dma_work)); - del_timer(&dreamcastcard->timer); dreamcastcard->substream = NULL; kfree(dreamcastcard->channel); spu_disable(); -- 2.17.1