virtio_fs: read the vring size under virtio_fs_mutex in ->get_tree

The vring size was read after virtio_fs_find_instance() had dropped
virtio_fs_mutex, so a concurrent virtio_fs_remove() could free the
virtqueue first. The reference from the lookup keeps the virtio_fs
alive, but not its virtqueues.

Hold the mutex across the lookup and the read.

This issue was found by an in-house static analysis tool.

Fixes: a7f0d7aab0b4 ("virtiofs: split requests that exceed virtqueue size")
Cc: stable@vger.kernel.org
Assisted-by: Codex:gpt-5.6
Co-developed-by: Song Li <songl@zju.edu.cn>
Signed-off-by: Song Li <songl@zju.edu.cn>
Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

0 files changed, 0 insertions, 0 deletions