linux-kernel - [PATCH AUTOSEL 4.19 07/11] scsi: core: Don't start concurrent async scan on same host

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20201103012039.183672-7-sashal@kernel.org>
Date:   Mon,  2 Nov 2020 20:20:35 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ming Lei <ming.lei@...hat.com>, Christoph Hellwig <hch@....de>,
        "Ewan D . Milne" <emilne@...hat.com>,
        Hannes Reinecke <hare@...e.de>,
        Bart Van Assche <bvanassche@....org>,
        Lee Duncan <lduncan@...e.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>, linux-scsi@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 07/11] scsi: core: Don't start concurrent async scan on same host

From: Ming Lei <ming.lei@...hat.com>

[ Upstream commit 831e3405c2a344018a18fcc2665acc5a38c3a707 ]

The current scanning mechanism is supposed to fall back to a synchronous
host scan if an asynchronous scan is in progress. However, this rule isn't
strictly respected, scsi_prep_async_scan() doesn't hold scan_mutex when
checking shost->async_scan. When scsi_scan_host() is called concurrently,
two async scans on same host can be started and a hang in do_scan_async()
is observed.

Fixes this issue by checking & setting shost->async_scan atomically with
shost->scan_mutex.

Link: https://lore.kernel.org/r/20201010032539.426615-1-ming.lei@redhat.com
Cc: Christoph Hellwig <hch@....de>
Cc: Ewan D. Milne <emilne@...hat.com>
Cc: Hannes Reinecke <hare@...e.de>
Cc: Bart Van Assche <bvanassche@....org>
Reviewed-by: Lee Duncan <lduncan@...e.com>
Reviewed-by: Bart Van Assche <bvanassche@....org>
Signed-off-by: Ming Lei <ming.lei@...hat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/scsi/scsi_scan.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 9a7e3a3bd5ce8..009a5b2aa3d02 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1722,15 +1722,16 @@ static void scsi_sysfs_add_devices(struct Scsi_Host *shost)
  */
 static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
 {
-	struct async_scan_data *data;
+	struct async_scan_data *data = NULL;
 	unsigned long flags;
 
 	if (strncmp(scsi_scan_type, "sync", 4) == 0)
 		return NULL;
 
+	mutex_lock(&shost->scan_mutex);
 	if (shost->async_scan) {
 		shost_printk(KERN_DEBUG, shost, "%s called twice\n", __func__);
-		return NULL;
+		goto err;
 	}
 
 	data = kmalloc(sizeof(*data), GFP_KERNEL);
@@ -1741,7 +1742,6 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
 		goto err;
 	init_completion(&data->prev_finished);
 
-	mutex_lock(&shost->scan_mutex);
 	spin_lock_irqsave(shost->host_lock, flags);
 	shost->async_scan = 1;
 	spin_unlock_irqrestore(shost->host_lock, flags);
@@ -1756,6 +1756,7 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
 	return data;
 
  err:
+	mutex_unlock(&shost->scan_mutex);
 	kfree(data);
 	return NULL;
 }
-- 
2.27.0