[dm-devel] dm-mq and end_clone_request()

[Bart Van Assche]

On 08/06/16 07:47, Laurence Oberman wrote:
> [66814.772851]  [<ffffffff8118e72f>] ? panic+0x1eb/0x233
> [66814.800207]  [<ffffffff810308f8>] oops_end+0xb8/0xd0
> [66814.827454]  [<ffffffff8106977e>] no_context+0x13e/0x3a0
> [66814.858368]  [<ffffffff811f3feb>] ? __slab_free+0x9b/0x280
> [66814.890365]  [<ffffffff81069ace>] __bad_area_nosemaphore+0xee/0x1d0
> [66814.926508]  [<ffffffff81069bc4>] bad_area_nosemaphore+0x14/0x20
> [66814.959939]  [<ffffffff8106a269>] __do_page_fault+0x89/0x4a0
> [66814.992039]  [<ffffffff811f3feb>] ? __slab_free+0x9b/0x280
> [66815.023052]  [<ffffffff8106a6b0>] do_page_fault+0x30/0x80
> [66815.053368]  [<ffffffff816c8b88>] page_fault+0x28/0x30
> [66815.083196]  [<ffffffff814ae4e9>] ? __scsi_remove_device+0x79/0x160
> [66815.117444]  [<ffffffff814ae5c2>] ? __scsi_remove_device+0x152/0x160
> [66815.152051]  [<ffffffff814ac790>] scsi_forget_host+0x60/0x70
> [66815.183939]  [<ffffffff814a0137>] scsi_remove_host+0x77/0x110
> [66815.216152]  [<ffffffffa0677be0>] srp_remove_work+0x90/0x200 [ib_srp]
> [66815.253221]  [<ffffffff810a2e72>] process_one_work+0x152/0x400
> [66815.286221]  [<ffffffff810a3765>] worker_thread+0x125/0x4b0
> [66815.317313]  [<ffffffff810a3640>] ? rescuer_thread+0x380/0x380
> [66815.349770]  [<ffffffff810a9298>] kthread+0xd8/0xf0
> [66815.376082]  [<ffffffff816c6b3f>] ret_from_fork+0x1f/0x40
> [66815.404767]  [<ffffffff810a91c0>] ? kthread_park+0x60/0x60

Hello Laurence and Johannes,

Later today I will start testing the following patch:


Subject: [PATCH] Fix a use-after-free in scsi_forget_host()

Avoid that scsi_forget_host() can call __scsi_remove_device()
while scsi_device_dev_release_usercontext() is freeing the same
SCSI device.
---
 drivers/scsi/scsi_scan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index e0a78f5..6cffc90 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1890,10 +1890,11 @@ void scsi_forget_host(struct Scsi_Host *shost)
  restart:
 	spin_lock_irqsave(shost->host_lock, flags);
 	list_for_each_entry(sdev, &shost->__devices, siblings) {
-		if (sdev->sdev_state == SDEV_DEL)
+		if (sdev->sdev_state == SDEV_DEL || scsi_device_get(sdev) < 0)
 			continue;
 		spin_unlock_irqrestore(shost->host_lock, flags);
 		__scsi_remove_device(sdev);
+		scsi_device_put(sdev);
 		goto restart;
 	}
 	spin_unlock_irqrestore(shost->host_lock, flags);
-- 
2.9.2