virtio-fs: avoid double-free on failed queue setup

Summary

In the Linux kernel, the following vulnerability has been resolved: virtio-fs: avoid double-free on failed queue setup virtio_fs_setup_vqs() allocates fs->vqs and fs->mq_map before calling virtio_find_vqs(). If virtio_find_vqs() fails, the error path frees both pointers and returns an error to virtio_fs_probe(). virtio_fs_probe() then drops the last kobject reference, and virtio_fs_ktype_release() frees fs->vqs and fs->mq_map again. This leaves dangling pointers in struct virtio_fs and can trigger a double-free during probe failure cleanup. Set fs->vqs and fs->mq_map to NULL immediately after kfree() in the virtio_fs_setup_vqs() error path so that the later kobject release sees an uninitialized state and kfree(NULL) becomes harmless. This can be reproduced when a broken virtio-fs device advertises more request queues than the transport actually provides. In that case virtio_find_vqs() fails while setting up the extra queue, and the probe path reaches the double-free cleanup sequence.

Timeline

1. Sep 24, 2026, 4:03 PM UTCCVE published
2. Sep 25, 2026, 12:43 PM UTCRecord last updated

Affected versions

• Linux Linux

  From a8f62f50b4e4ea92a938fca2ec1bd108d7f210e9 · fixed in 3fbc5ee776fefbc6ea34d2518f1f5f90aa2e1dad; From a8f62f50b4e4ea92a938fca2ec1bd108d7f210e9 · fixed in 20ef4739b329bb09cff11dd2458795a50674658e; From a8f62f50b4e4ea92a938fca2ec1bd108d7f210e9 · fixed in 6af3330ec5d5fb8c06c04eb520a71cf73ea5a765

• Linux Linux

  6.9

• KernelLinux

  From 6.9.0 · fixed in 6.12.111; From 6.13.0 · fixed in 6.18.53

References 3