CVE-2022-48890 — scsi: storvsc: Fix swiotlb bounce buffer leak in confidential VM

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

scsi: storvsc: Fix swiotlb bounce buffer leak in confidential VM

storvsc_queuecommand() maps the scatter/gather list using scsi_dma_map(), which in a confidential VM allocates swiotlb bounce buffers. If the I/O submission fails in storvsc_do_io(), the I/O is typically retried by higher level code, but the bounce buffer memory is never freed. The mostly like cause of I/O submission failure is a full VMBus channel ring buffer, which is not uncommon under high I/O loads. Eventually enough bounce buffer memory leaks that the confidential VM can't do any I/O. The same problem can arise in a non-confidential VM with kernel boot parameter swiotlb=force.

Fix this by doing scsi_dma_unmap() in the case of an I/O submission error, which frees the bounce buffer memory.

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CVE-2022-48890 — scsi: storvsc: Fix swiotlb bounce buffer leak in confidential VM