| Message ID | 1670183564-76254-1-git-send-email-mikelley@microsoft.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [1/1] scsi: storvsc: Fix swiotlb bounce buffer leak in confidential VM | expand |
> From: Michael Kelley (LINUX) <mikelley@microsoft.com> > Sent: Sunday, December 4, 2022 11:53 AM > > 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> > --- Reviewed-by: Dexuan Cui <decui@microsoft.com> Tested-by: Dexuan Cui <decui@microsoft.com> I hope this fix can be included in v6.1.
On 12/5/2022 3:52 AM, Michael Kelley wrote: > 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> Nice catch! Thanks to fix this. Reviewed-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Michael, > 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. Applied to 6.2/scsi-staging, thanks!
diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index 3c5b7e4..55d6fb4 100644 --- a/drivers/scsi/storvsc_drv.c +++ b/drivers/scsi/storvsc_drv.c @@ -1823,6 +1823,9 @@ 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;
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> --- drivers/scsi/storvsc_drv.c | 3 +++ 1 file changed, 3 insertions(+)