diff options
authorAlex Williamson <alex.williamson@redhat.com>2019-04-03 12:36:21 -0600
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-05-04 08:49:10 +0200
commit4f97abd571ec3d56c50a2edfe0932059f4549afa (patch)
parentb491c6f370eaac686161a0cb5cefc93a875dafed (diff)
vfio/type1: Limit DMA mappings per container
commit 492855939bdb59c6f947b0b5b44af9ad82b7e38c upstream. Memory backed DMA mappings are accounted against a user's locked memory limit, including multiple mappings of the same memory. This accounting bounds the number of such mappings that a user can create. However, DMA mappings that are not backed by memory, such as DMA mappings of device MMIO via mmaps, do not make use of page pinning and therefore do not count against the user's locked memory limit. These mappings still consume memory, but the memory is not well associated to the process for the purpose of oom killing a task. To add bounding on this use case, we introduce a limit to the total number of concurrent DMA mappings that a user is allowed to create. This limit is exposed as a tunable module option where the default value of 64K is expected to be well in excess of any reasonable use case (a large virtual machine configuration would typically only make use of tens of concurrent mappings). This fixes CVE-2019-3882. Reviewed-by: Eric Auger <eric.auger@redhat.com> Tested-by: Eric Auger <eric.auger@redhat.com> Reviewed-by: Peter Xu <peterx@redhat.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Signed-off-by: Alex Williamson <alex.williamson@redhat.com> [groeck: Adjust for missing upstream commit] Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 14 insertions, 0 deletions
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 1d48e62f4f52..0d5b667c0e65 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -53,10 +53,16 @@ module_param_named(disable_hugepages,
"Disable VFIO IOMMU support for IOMMU hugepages.");
+static unsigned int dma_entry_limit __read_mostly = U16_MAX;
+module_param_named(dma_entry_limit, dma_entry_limit, uint, 0644);
+ "Maximum number of user DMA mappings per container (65535).");
struct vfio_iommu {
struct list_head domain_list;
struct mutex lock;
struct rb_root dma_list;
+ unsigned int dma_avail;
bool v2;
bool nesting;
@@ -384,6 +390,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
vfio_unmap_unpin(iommu, dma);
vfio_unlink_dma(iommu, dma);
+ iommu->dma_avail++;
static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
@@ -584,12 +591,18 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
return -EEXIST;
+ if (!iommu->dma_avail) {
+ mutex_unlock(&iommu->lock);
+ return -ENOSPC;
+ }
dma = kzalloc(sizeof(*dma), GFP_KERNEL);
if (!dma) {
return -ENOMEM;
+ iommu->dma_avail--;
dma->iova = iova;
dma->vaddr = vaddr;
dma->prot = prot;
@@ -905,6 +918,7 @@ static void *vfio_iommu_type1_open(unsigned long arg)
iommu->dma_list = RB_ROOT;
+ iommu->dma_avail = dma_entry_limit;
return iommu;

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