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Wed, 05 Oct 2022 10:48:34 -0700 (PDT) From: Oleksandr Tyshchenko To: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Cc: Oleksandr Tyshchenko , Stefano Stabellini , Juergen Gross Subject: [PATCH 2/2] xen/virtio: Fix potential deadlock when accessing xen_grant_dma_devices Date: Wed, 5 Oct 2022 20:48:23 +0300 Message-Id: <20221005174823.1800761-3-olekstysh@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20221005174823.1800761-1-olekstysh@gmail.com> References: <20221005174823.1800761-1-olekstysh@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @gmail.com) X-ZM-MESSAGEID: 1664992152197100001 Content-Type: text/plain; charset="utf-8" From: Oleksandr Tyshchenko 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 Fixes: d6aca3504c7d ("xen/grant-dma-ops: Add option to restrict memory acce= ss under Xen") Reviewed-by: Juergen Gross Reviewed-by: Stefano Stabellini --- 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; }; =20 -static DEFINE_XARRAY(xen_grant_dma_devices); +static DEFINE_XARRAY_FLAGS(xen_grant_dma_devices, XA_FLAGS_LOCK_IRQ); =20 #define XEN_GRANT_DMA_ADDR_OFF (1ULL << 63) =20 @@ -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 *d= ev) { struct xen_grant_dma_data *data; + unsigned long flags; =20 - xa_lock(&xen_grant_dma_devices); + xa_lock_irqsave(&xen_grant_dma_devices, flags); data =3D xa_load(&xen_grant_dma_devices, (unsigned long)dev); - xa_unlock(&xen_grant_dma_devices); + xa_unlock_irqrestore(&xen_grant_dma_devices, flags); =20 return data; } =20 +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 =3D xa_err(__xa_store(&xen_grant_dma_devices, (unsigned long)dev, dat= a, + 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 =3D iommu_spec.args[0]; =20 - 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; } --=20 2.25.1