On 2018-11-07 1:18 pm, Geert Uytterhoeven wrote:
If iommu_ops.add_device() fails, iommu_ops.domain_free() is still
called, leading to a crash, as the domain was only partially
initialized:

     ipmmu-vmsa e67b0000.mmu: Cannot accommodate DMA translation for IOMMU page 
tables
     sata_rcar ee300000.sata: Unable to initialize IPMMU context
     iommu: Failed to add device ee300000.sata to group 0: -22
     Unable to handle kernel NULL pointer dereference at virtual address 
0000000000000038
     ...
     Call trace:
      ipmmu_domain_free+0x1c/0xa0
      iommu_group_release+0x48/0x68
      kobject_put+0x74/0xe8
      kobject_del.part.0+0x3c/0x50
      kobject_put+0x60/0xe8
      iommu_group_get_for_dev+0xa8/0x1f0
      ipmmu_add_device+0x1c/0x40
      of_iommu_configure+0x118/0x190

Fix this by checking if the domain's context already exists, before
trying to destroy it.

Reviewed-by: Robin Murphy <[email protected]>

Signed-off-by: Geert Uytterhoeven <[email protected]>
---
  drivers/iommu/ipmmu-vmsa.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/ipmmu-vmsa.c b/drivers/iommu/ipmmu-vmsa.c
index c4114b92652eb0c9..a8b2c649c1d1f1b9 100644
--- a/drivers/iommu/ipmmu-vmsa.c
+++ b/drivers/iommu/ipmmu-vmsa.c
@@ -498,6 +498,9 @@ static int ipmmu_domain_init_context(struct 
ipmmu_vmsa_domain *domain)
static void ipmmu_domain_destroy_context(struct ipmmu_vmsa_domain *domain)
  {
+       if (!domain->mmu)
+               return;
+
        /*
         * Disable the context. Flush the TLB as required when modifying the
         * context registers.

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