Hi, The virtio-pmem flush path uses a virtqueue cookie/token to carry a per-request context through completion. Under broken virtqueue / notify failure conditions, the submitter can return and free the request object while the host/backend may still complete the published request. The IRQ completion handler then dereferences freed memory when waking waiters, which is reported by KASAN as a slab-use-after-free and may manifest as lock corruption (e.g. "BUG: spinlock already unlocked") without KASAN.
In addition, the flush path has two wait sites: one for virtqueue descriptor availability (-ENOSPC from virtqueue_add_sgs()) and one for request completion. If the virtqueue becomes broken, forward progress is no longer guaranteed and these waiters may sleep indefinitely unless the driver converges the failure and wakes all wait sites. This series addresses both issues: 1/5 nvdimm: virtio_pmem: always wake -ENOSPC waiters Wake one -ENOSPC waiter for each reclaimed used buffer, decoupled from token completion. 2/5 nvdimm: virtio_pmem: use READ_ONCE()/WRITE_ONCE() for wait flags Use READ_ONCE()/WRITE_ONCE() for the wait_event() flags (done and wq_buf_avail). 3/5 nvdimm: virtio_pmem: refcount requests for token lifetime Refcount request objects so the token lifetime spans the window where it is reachable through the virtqueue until completion/drain drops the virtqueue reference. 4/5 nvdimm: virtio_pmem: converge broken virtqueue to -EIO Track a device-level broken state to converge broken/notify failures to -EIO: wake all waiters and drain/detach outstanding requests to complete them with an error, and fail-fast new requests. 5/5 nvdimm: virtio_pmem: drain requests in freeze Drain outstanding requests in freeze() before tearing down virtqueues so waiters do not sleep indefinitely. Testing was done on QEMU x86_64 with a virtio-pmem device exported as /dev/pmem0, formatted with ext4 (-O fast_commit), mounted with DAX, and stressed with fsync-heavy workloads. Thanks, Li Chen Changelog: v2->v3: - Split patch 1 as suggested by Pankaj Gupta: keep the waiter wakeup ordering change in 1/5 and move READ_ONCE()/WRITE_ONCE() updates to 2/5 (no functional change intended). - Add log report to commit msg - Fold the export fix into 4/5 to keep the series bisectable when CONFIG_VIRTIO_PMEM=m. v1->v2: add the export patch to fix compile issue. Links: v2: https://lore.kernel.org/all/[email protected]/ Li Chen (5): nvdimm: virtio_pmem: always wake -ENOSPC waiters nvdimm: virtio_pmem: use READ_ONCE()/WRITE_ONCE() for wait flags nvdimm: virtio_pmem: refcount requests for token lifetime nvdimm: virtio_pmem: converge broken virtqueue to -EIO nvdimm: virtio_pmem: drain requests in freeze drivers/nvdimm/nd_virtio.c | 137 +++++++++++++++++++++++++++++------ drivers/nvdimm/virtio_pmem.c | 14 ++++ drivers/nvdimm/virtio_pmem.h | 6 ++ 3 files changed, 136 insertions(+), 21 deletions(-) -- 2.52.0
