From 67ff3d0a49f3d445c3922e30a54e03c161da561e Mon Sep 17 00:00:00 2001
From: Michael Kelley <mikelley@microsoft.com>
Date: Sun, 4 Dec 2022 11:52:44 -0800
Subject: [PATCH] scsi: storvsc: Fix swiotlb bounce buffer leak in confidential
VM
References: bsc#1206006
Git-commit: 67ff3d0a49f3d445c3922e30a54e03c161da561e
Patch-mainline: v6.2-rc4
storvsc_queuecommand() maps the scatter/gather list using scsi_dma_map(),
which in a confidential VM allocates swiotlb bounce buffers. If the I/O
submission fails in storvsc_do_io(), the I/O is typically retried by higher
level code, but the bounce buffer memory is never freed. The mostly like
cause of I/O submission failure is a full VMBus channel ring buffer, which
is not uncommon under high I/O loads. Eventually enough bounce buffer
memory leaks that the confidential VM can't do any I/O. The same problem
can arise in a non-confidential VM with kernel boot parameter
swiotlb=force.
Fix this by doing scsi_dma_unmap() in the case of an I/O submission
error, which frees the bounce buffer memory.
Fixes: 743b237c3a7b ("scsi: storvsc: Add Isolation VM support for storvsc driver")
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1670183564-76254-1-git-send-email-mikelley@microsoft.com
Tested-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Thomas Abraham <tabraham@suse.com>
---
drivers/scsi/storvsc_drv.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index a84194d82347..0252ee2dd844 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1824,6 +1824,9 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
ret = storvsc_do_io(dev, cmd_request, get_cpu());
put_cpu();
+ if (ret)
+ scsi_dma_unmap(scmnd);
+
if (ret == -EAGAIN) {
/* no more space */
ret = SCSI_MLQUEUE_DEVICE_BUSY;
--
2.35.3