On Fri, Oct 14, 2022 at 03:25:41PM -0700, Fenghua Yu wrote: > When the idxd_user_drv driver is bound to a Work Queue (WQ) device > without IOMMU or with IOMMU Passthrough without Shared Virtual > Addressing (SVA), the application gains direct access to physical > memory via the device by programming physical address to a submitted > descriptor. This allows direct userspace read and write access to > arbitrary physical memory. This is inconsistent with the security > goals of a good kernel API. > > Unlike vfio_pci driver, the IDXD char device driver does not provide any > ways to pin user pages and translate the address from user VA to IOVA or > PA without IOMMU SVA. Therefore the application has no way to instruct the > device to perform DMA function. This makes the char device not usable for > normal application usage. > > Since user type WQ without SVA cannot be used for normal application usage > and presents the security issue, bind idxd_user_drv driver and enable user > type WQ only when SVA is enabled (i.e. user PASID is enabled). > > Fixes: 448c3de8ac83 ("dmaengine: idxd: create user driver for wq 'device'") > Cc: stable@xxxxxxxxxxxxxxx > Suggested-by: Arjan Van De Ven <arjan.van.de.ven@xxxxxxxxx> > Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx> > Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx> Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx> > --- > v2: > - Update changlog per Dave Hansen's comments > > drivers/dma/idxd/cdev.c | 18 ++++++++++++++++++ > include/uapi/linux/idxd.h | 1 + > 2 files changed, 19 insertions(+) > > diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c > index c2808fd081d6..a9b96b18772f 100644 > --- a/drivers/dma/idxd/cdev.c > +++ b/drivers/dma/idxd/cdev.c > @@ -312,6 +312,24 @@ static int idxd_user_drv_probe(struct idxd_dev *idxd_dev) > if (idxd->state != IDXD_DEV_ENABLED) > return -ENXIO; > > + /* > + * User type WQ is enabled only when SVA is enabled for two reasons: > + * - If no IOMMU or IOMMU Passthrough without SVA, userspace > + * can directly access physical address through the WQ. > + * - The IDXD cdev driver does not provide any ways to pin > + * user pages and translate the address from user VA to IOVA or > + * PA without IOMMU SVA. Therefore the application has no way > + * to instruct the device to perform DMA function. This makes > + * the cdev not usable for normal application usage. > + */ > + if (!device_user_pasid_enabled(idxd)) { > + idxd->cmd_status = IDXD_SCMD_WQ_USER_NO_IOMMU; > + dev_dbg(&idxd->pdev->dev, > + "User type WQ cannot be enabled without SVA.\n"); > + > + return -EOPNOTSUPP; > + } > + > mutex_lock(&wq->wq_lock); > wq->type = IDXD_WQT_USER; > rc = drv_enable_wq(wq); > diff --git a/include/uapi/linux/idxd.h b/include/uapi/linux/idxd.h > index 095299c75828..2b9e7feba3f3 100644 > --- a/include/uapi/linux/idxd.h > +++ b/include/uapi/linux/idxd.h > @@ -29,6 +29,7 @@ enum idxd_scmd_stat { > IDXD_SCMD_WQ_NO_SIZE = 0x800e0000, > IDXD_SCMD_WQ_NO_PRIV = 0x800f0000, > IDXD_SCMD_WQ_IRQ_ERR = 0x80100000, > + IDXD_SCMD_WQ_USER_NO_IOMMU = 0x80110000, > }; > > #define IDXD_SCMD_SOFTERR_MASK 0x80000000 > -- > 2.32.0 >