disk_*: handle out of range accesses #415
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Currently, the SCSI and NVMe emulators validate that a read/write/unmap is in range before calling down to the backing disks. This creates a TOCTOU problem because the disk size can change at any time, asynchronously from any IO. It also creates additional synchronization headaches since the disk implementations must be able to provide the up-to-date disk size efficiently. As a first step, add this range checking in the various disk implementations. A subsequent change can remove the redundant checks in the NVMe and SCSI emulators.
daprilik
approved these changes
Dec 2, 2024
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Currently, the SCSI and NVMe emulators validate that a read/write/unmap is in range before calling down to the backing disks. This creates a TOCTOU problem because the disk size can change at any time, asynchronously from any IO. It also creates additional synchronization headaches since the disk implementations must be able to provide the up-to-date disk size efficiently.
As a first step, add this range checking in the various disk implementations. A subsequent change can remove the redundant checks in the NVMe and SCSI emulators.