AMD IOMMU: fix possible race while accessing iommu->need_sync

The access to the iommu->need_sync member needs to be protected by the
iommu->lock. Otherwise this is a possible race condition. Fix it with
this patch.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 13 insertions, 20 deletions

diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index a232e5a85d4..5662e226b0c 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -187,6 +187,8 @@ static int iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd)
 
         spin_lock_irqsave(&iommu->lock, flags);
         ret = __iommu_queue_command(iommu, cmd);
+        if (!ret)
+                iommu->need_sync = 1;
         spin_unlock_irqrestore(&iommu->lock, flags);
 
         return ret;
@@ -210,10 +212,13 @@ static int iommu_completion_wait(struct amd_iommu *iommu)
         cmd.data[0] = CMD_COMPL_WAIT_INT_MASK;
         CMD_SET_TYPE(&cmd, CMD_COMPL_WAIT);
 
-        iommu->need_sync = 0;
-
         spin_lock_irqsave(&iommu->lock, flags);
 
+        if (!iommu->need_sync)
+                goto out;
+
+        iommu->need_sync = 0;
+
         ret = __iommu_queue_command(iommu, &cmd);
 
         if (ret)
@@ -254,8 +259,6 @@ static int iommu_queue_inv_dev_entry(struct amd_iommu *iommu, u16 devid)
 
         ret = iommu_queue_command(iommu, &cmd);
 
-        iommu->need_sync = 1;
-
         return ret;
 }
 
@@ -281,8 +284,6 @@ static int iommu_queue_inv_iommu_pages(struct amd_iommu *iommu,
 
         ret = iommu_queue_command(iommu, &cmd);
 
-        iommu->need_sync = 1;
-
         return ret;
 }
 
@@ -762,8 +763,6 @@ static void set_device_domain(struct amd_iommu *iommu,
         write_unlock_irqrestore(&amd_iommu_devtable_lock, flags);
 
         iommu_queue_inv_dev_entry(iommu, devid);
-
-        iommu->need_sync = 1;
 }
 
 /*****************************************************************************
@@ -1034,8 +1033,7 @@ static dma_addr_t map_single(struct device *dev, phys_addr_t paddr,
         if (addr == bad_dma_address)
                 goto out;
 
-        if (unlikely(iommu->need_sync))
-                iommu_completion_wait(iommu);
+        iommu_completion_wait(iommu);
 
 out:
         spin_unlock_irqrestore(&domain->lock, flags);
@@ -1063,8 +1061,7 @@ static void unmap_single(struct device *dev, dma_addr_t dma_addr,
 
         __unmap_single(iommu, domain->priv, dma_addr, size, dir);
 
-        if (unlikely(iommu->need_sync))
-                iommu_completion_wait(iommu);
+        iommu_completion_wait(iommu);
 
         spin_unlock_irqrestore(&domain->lock, flags);
 }
@@ -1130,8 +1127,7 @@ static int map_sg(struct device *dev, struct scatterlist *sglist,
                         goto unmap;
         }
 
-        if (unlikely(iommu->need_sync))
-                iommu_completion_wait(iommu);
+        iommu_completion_wait(iommu);
 
 out:
         spin_unlock_irqrestore(&domain->lock, flags);
@@ -1176,8 +1172,7 @@ static void unmap_sg(struct device *dev, struct scatterlist *sglist,
                 s->dma_address = s->dma_length = 0;
         }
 
-        if (unlikely(iommu->need_sync))
-                iommu_completion_wait(iommu);
+        iommu_completion_wait(iommu);
 
         spin_unlock_irqrestore(&domain->lock, flags);
 }
@@ -1228,8 +1223,7 @@ static void *alloc_coherent(struct device *dev, size_t size,
                 goto out;
         }
 
-        if (unlikely(iommu->need_sync))
-                iommu_completion_wait(iommu);
+        iommu_completion_wait(iommu);
 
 out:
         spin_unlock_irqrestore(&domain->lock, flags);
@@ -1260,8 +1254,7 @@ static void free_coherent(struct device *dev, size_t size,
 
         __unmap_single(iommu, domain->priv, dma_addr, size, DMA_BIDIRECTIONAL);
 
-        if (unlikely(iommu->need_sync))
-                iommu_completion_wait(iommu);
+        iommu_completion_wait(iommu);
 
         spin_unlock_irqrestore(&domain->lock, flags);