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| author | Philippe Mathieu-Daudé <philmd@redhat.com> | 2021-07-23 21:58:43 +0200 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2021-07-26 09:38:12 +0100 |
| commit | 15a730e7a3aaac180df72cd5730e0617bcf44a5a (patch) | |
| tree | 00c4dc76484b587c85b29173c6a70ad5e132908b /block/nvme.c | |
| parent | a2376507f615495b1d16685449ce0ea78c2caf9d (diff) | |
| download | qemu-15a730e7a3aaac180df72cd5730e0617bcf44a5a.zip | |
block/nvme: Fix VFIO_MAP_DMA failed: No space left on device
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) c
VFIO_MAP_DMA failed: No space left on device
(The VM is not resumable from here, hence stuck.)
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-stable@nongnu.org
Cc: Fam Zheng <fam@euphon.net>
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Reported-by: Michal Prívozník <mprivozn@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20210723195843.1032825-1-philmd@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 <philmd@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'block/nvme.c')
| -rw-r--r-- | block/nvme.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/block/nvme.c b/block/nvme.c index 2b5421e7aa..e8dbbc2317 100644 --- a/block/nvme.c +++ b/block/nvme.c @@ -1030,7 +1030,29 @@ try_map: r = qemu_vfio_dma_map(s->vfio, qiov->iov[i].iov_base, len, true, &iova); + if (r == -ENOSPC) { + /* + * In addition to the -ENOMEM error, the VFIO_IOMMU_MAP_DMA + * ioctl returns -ENOSPC to signal the user exhausted the DMA + * mappings available for a container since Linux kernel commit + * 492855939bdb ("vfio/type1: Limit DMA mappings per container", + * April 2019, see CVE-2019-3882). + * + * This block driver already handles this error path by checking + * for the -ENOMEM error, so we directly replace -ENOSPC by + * -ENOMEM. Beside, -ENOSPC has a specific meaning for blockdev + * coroutines: it triggers BLOCKDEV_ON_ERROR_ENOSPC and + * BLOCK_ERROR_ACTION_STOP which stops the VM, asking the operator + * to add more storage to the blockdev. Not something we can do + * easily with an IOMMU :) + */ + r = -ENOMEM; + } if (r == -ENOMEM && retry) { + /* + * We exhausted the DMA mappings available for our container: + * recycle the volatile IOVA mappings. + */ retry = false; trace_nvme_dma_flush_queue_wait(s); if (s->dma_map_count) { |