Re: [syzbot] test uaf in iommufd_vfio_ioas

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@xxxxxxxxxxxxxxx.

***

Subject: test uaf in iommufd_vfio_ioas
Author: lizhi.xu@xxxxxxxxxxxxx

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2af9b20dbb39

diff --git a/drivers/iommu/iommufd/vfio_compat.c b/drivers/iommu/iommufd/vfio_compat.c
index 6c810bf80f99..85cff4489757 100644
--- a/drivers/iommu/iommufd/vfio_compat.c
+++ b/drivers/iommu/iommufd/vfio_compat.c
@@ -138,6 +138,8 @@ int iommufd_vfio_ioas(struct iommufd_ucmd *ucmd)
 
 	case IOMMU_VFIO_IOAS_SET:
 		ioas = iommufd_get_ioas(ucmd->ictx, cmd->ioas_id);
+		if (!ioas)
+			return -EINVAL;
 		if (IS_ERR(ioas))
 			return PTR_ERR(ioas);
 		xa_lock(&ucmd->ictx->objects);