When the NVMe block driver was introduced (see commit bdd6a90a9e5, January 2018), Linux VFIO_IOMMU_MAP_DMA ioctl was only returning -ENOMEM in case of error. The driver was correctly handling the error path to recycle its volatile IOVA mappings.
To fix CVE-2019-3882, Linux commit 492855939bdb ("vfio/type1: Limit DMA mappings per container", April 2019) added the -ENOSPC error to signal the user exhausted the DMA mappings available for a container. The block driver started to mis-behave: qemu-system-x86_64: VFIO_MAP_DMA failed: No space left on device (qemu) (qemu) info status VM status: paused (io-error) (qemu) c VFIO_MAP_DMA failed: No space left on device qemu-system-x86_64: block/block-backend.c:1968: blk_get_aio_context: Assertion `ctx == blk->ctx' failed. Fix by handling the new -ENOSPC error (when DMA mappings are exhausted) without any distinction to the current -ENOMEM error, so we don't change the behavior on old kernels where the CVE-2019-3882 fix is not present. An easy way to reproduce this bug is to restrict the DMA mapping limit (65535 by default) when loading the VFIO IOMMU module: # modprobe vfio_iommu_type1 dma_entry_limit=666 Cc: qemu-sta...@nongnu.org Reported-by: Michal Prívozník <mpriv...@redhat.com> Fixes: bdd6a90a9e5 ("block: Add VFIO based NVMe driver") Buglink: https://bugs.launchpad.net/qemu/+bug/1863333 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/65 Signed-off-by: Philippe Mathieu-Daudé <phi...@redhat.com> --- v2: KISS checking both errors undistinguishedly (Maxim) --- block/nvme.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/nvme.c b/block/nvme.c index 2b5421e7aa6..c3d2a49866c 100644 --- a/block/nvme.c +++ b/block/nvme.c @@ -1030,7 +1030,7 @@ try_map: r = qemu_vfio_dma_map(s->vfio, qiov->iov[i].iov_base, len, true, &iova); - if (r == -ENOMEM && retry) { + if ((r == -ENOMEM || r == -ENOSPC) && retry) { retry = false; trace_nvme_dma_flush_queue_wait(s); if (s->dma_map_count) { -- 2.31.1