[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 2/2] xen/virtio: Fix potential deadlock when accessing xen_grant_dma_devices
On Wed, 5 Oct 2022, Oleksandr Tyshchenko wrote: > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> > > As find_xen_grant_dma_data() is called from both interrupt and process > contexts, the access to xen_grant_dma_devices XArray must be protected > by xa_lock_irqsave to avoid deadlock scenario. > As XArray API doesn't provide xa_store_irqsave helper, call lockless > __xa_store directly and guard it externally. > > Also move the storage of the XArray's entry to a separate helper. > > Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> > Fixes: d6aca3504c7d ("xen/grant-dma-ops: Add option to restrict memory access > under Xen") Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx> > --- > drivers/xen/grant-dma-ops.c | 24 +++++++++++++++++++----- > 1 file changed, 19 insertions(+), 5 deletions(-) > > diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c > index 1998d0e8ce82..c66f56d24013 100644 > --- a/drivers/xen/grant-dma-ops.c > +++ b/drivers/xen/grant-dma-ops.c > @@ -25,7 +25,7 @@ struct xen_grant_dma_data { > bool broken; > }; > > -static DEFINE_XARRAY(xen_grant_dma_devices); > +static DEFINE_XARRAY_FLAGS(xen_grant_dma_devices, XA_FLAGS_LOCK_IRQ); > > #define XEN_GRANT_DMA_ADDR_OFF (1ULL << 63) > > @@ -42,14 +42,29 @@ static inline grant_ref_t dma_to_grant(dma_addr_t dma) > static struct xen_grant_dma_data *find_xen_grant_dma_data(struct device *dev) > { > struct xen_grant_dma_data *data; > + unsigned long flags; > > - xa_lock(&xen_grant_dma_devices); > + xa_lock_irqsave(&xen_grant_dma_devices, flags); > data = xa_load(&xen_grant_dma_devices, (unsigned long)dev); > - xa_unlock(&xen_grant_dma_devices); > + xa_unlock_irqrestore(&xen_grant_dma_devices, flags); > > return data; > } > > +static int store_xen_grant_dma_data(struct device *dev, > + struct xen_grant_dma_data *data) > +{ > + unsigned long flags; > + int ret; > + > + xa_lock_irqsave(&xen_grant_dma_devices, flags); > + ret = xa_err(__xa_store(&xen_grant_dma_devices, (unsigned long)dev, > data, > + GFP_ATOMIC)); > + xa_unlock_irqrestore(&xen_grant_dma_devices, flags); > + > + return ret; > +} > + > /* > * DMA ops for Xen frontends (e.g. virtio). > * > @@ -338,8 +353,7 @@ void xen_grant_setup_dma_ops(struct device *dev) > */ > data->backend_domid = iommu_spec.args[0]; > > - if (xa_err(xa_store(&xen_grant_dma_devices, (unsigned long)dev, data, > - GFP_KERNEL))) { > + if (store_xen_grant_dma_data(dev, data)) { > dev_err(dev, "Cannot store Xen grant DMA data\n"); > goto err; > } > -- > 2.25.1 >
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