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xen/virtio: Fix potential deadlock when accessing xen_grant_dma_devices

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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.

Fixes: d6aca3504c ("xen/grant-dma-ops: Add option to restrict memory access under Xen")
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20221005174823.1800761-3-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Oleksandr Tyshchenko 2022-10-05 20:48:23 +03:00 • committed by Juergen Gross
parent e433715b11
commit 77be00f194
1 changed files with 19 additions and 5 deletions
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24
drivers/xen/grant-dma-ops.c
View file

@ -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;
}