[PATCH] iommu/dma: Fix race condition during iova_domain initialization

[yf.wang]

From: Yunfei Wang <yf.wang@xxxxxxxxxxxx>

When many devices share the same iova domain, iommu_dma_init_domain()
may be called at the same time. The checking of iovad->start_pfn will
all get false in iommu_dma_init_domain() and both enter init_iova_domain()
to do iovad initialization.

Fix this by protecting init_iova_domain() with iommu_dma_cookie->mutex.

Exception backtrace:
rb_insert_color(param1=0xFFFFFF80CD2BDB40, param3=1) + 64
init_iova_domain() + 180
iommu_setup_dma_ops() + 260
arch_setup_dma_ops() + 132
of_dma_configure_id() + 468
platform_dma_configure() + 32
really_probe() + 1168
driver_probe_device() + 268
__device_attach_driver() + 524
__device_attach() + 524
bus_probe_device() + 64
deferred_probe_work_func() + 260
process_one_work() + 580
worker_thread() + 1076
kthread() + 332
ret_from_fork() + 16

Signed-off-by: Ning Li <ning.li@xxxxxxxxxxxx>
Signed-off-by: Yunfei Wang <yf.wang@xxxxxxxxxxxx>
---
 drivers/iommu/dma-iommu.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 09f6e1c0f9c0..b38c5041eeab 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -63,6 +63,7 @@ struct iommu_dma_cookie {
 
 	/* Domain for flush queue callback; NULL if flush queue not in use */
 	struct iommu_domain		*fq_domain;
+	struct mutex			mutex;
 };
 
 static DEFINE_STATIC_KEY_FALSE(iommu_deferred_attach_enabled);
@@ -309,6 +310,7 @@ int iommu_get_dma_cookie(struct iommu_domain *domain)
 	if (!domain->iova_cookie)
 		return -ENOMEM;
 
+	mutex_init(&domain->iova_cookie->mutex);
 	return 0;
 }
 
@@ -549,26 +551,33 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
 	}
 
 	/* start_pfn is always nonzero for an already-initialised domain */
+	mutex_lock(&cookie->mutex);
 	if (iovad->start_pfn) {
 		if (1UL << order != iovad->granule ||
 		    base_pfn != iovad->start_pfn) {
 			pr_warn("Incompatible range for DMA domain\n");
-			return -EFAULT;
+			ret = -EFAULT;
+			goto done_unlock;
 		}
 
-		return 0;
+		ret = 0;
+		goto done_unlock;
 	}
 
 	init_iova_domain(iovad, 1UL << order, base_pfn);
 	ret = iova_domain_init_rcaches(iovad);
 	if (ret)
-		return ret;
+		goto done_unlock;
 
 	/* If the FQ fails we can simply fall back to strict mode */
 	if (domain->type == IOMMU_DOMAIN_DMA_FQ && iommu_dma_init_fq(domain))
 		domain->type = IOMMU_DOMAIN_DMA;
 
-	return iova_reserve_iommu_regions(dev, domain);
+	ret = iova_reserve_iommu_regions(dev, domain);
+
+done_unlock:
+	mutex_unlock(&cookie->mutex);
+	return ret;
 }
 
 /**
-- 
2.18.0