KVM: PPC: Book3S HV: fix secure device page leak on uv_page_in() failure

Overview

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

KVM: PPC: Book3S HV: fix secure device page leak on uv_page_in() failure

In kvmppc_svm_page_in(), if uv_page_in() fails after kvmppc_uvmem_get_page() has succeeded, the secure device page is never released. kvmppc_uvmem_get_page() sets a bit in kvmppc_uvmem_bitmap, allocates a kvmppc_uvmem_page_pvt struct, marks the GFN as KVMPPC_GFN_UVMEM_PFN, and calls zone_device_page_init() which sets refcount=1 and locks the page. The subsequent goto out_finalize skips the *mig.dst assignment, so migrate_vma_finalize() is a no-op for the page, and none of those resources are ever reclaimed.

Each occurrence permanently consumes one entry from the firmware-bounded secure memory pool (kvmppc_uvmem_bitmap), leaks pvt, and leaves the GFN marked as secure — making it unusable for the lifetime of the VM.

The twin __kvmppc_svm_page_out() already handles the analogous uv_page_out() failure correctly with unlock_page(dpage); __free_page(dpage). Apply the same pattern here: unlock_page() followed by put_page(), which chains through free_zone_device_folio() into kvmppc_uvmem_folio_free() to clear the bitmap bit, free pvt, and reset the GFN state.

Reachable whenever uv_page_in() returns an error (e.g. UV pool exhaustion) on any POWER9/10 + Ultravisor/PEF system.

Affected

• Linux >= ca9f4942670c37407bb109090eaf776ce2ccc54c < ed2f2ff63cb7e71204096e765c6d02c3b6974b95
• Linux >= ca9f4942670c37407bb109090eaf776ce2ccc54c < 8f3b7746874b39fc20e0363c9076c7787d4765ba
• Linux >= ca9f4942670c37407bb109090eaf776ce2ccc54c < a933d7024359e2e566b07903d1294b84f90482ae
• Linux >= ca9f4942670c37407bb109090eaf776ce2ccc54c < c41088b2765af1e97e7bb05f906ae1823eca0388
• Linux >= ca9f4942670c37407bb109090eaf776ce2ccc54c < f3d4b2fc30c97cf8e6f8b880d2de9c17ecac7f5b
• Linux >= ca9f4942670c37407bb109090eaf776ce2ccc54c < dfb84274932737e338ff5eb27f34b4c8ecb01b50
• Linux >= ca9f4942670c37407bb109090eaf776ce2ccc54c < fcbff8008b0e08cd53b611bd0ff7e01f5b962f80
• Linux >= ca9f4942670c37407bb109090eaf776ce2ccc54c < 0a416ee20bcccddf91ca5b63696a23b9d11d73aa
• Linux 5.5

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.