CVE-2022-48890

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 cant 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.

Weakness

The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/67ff3d0a49f3d445c3922e30a54e03c161da561e
• https://git.kernel.org/stable/c/87c71e88f6a6619ffb1ff88f84dff48ef6d57adb