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load_unaligned_zeropad() can lead to unwanted loads across page boundaries. The unwanted loads are typically harmless. But, they might be made to totally unrelated or even unmapped memory. load_unaligned_zeropad() relies on exception fixup (#PF, #GP and now #VE) to recover from these unwanted loads. In TDX guests, the second page can be shared page and a VMM may configure it to trigger #VE. The kernel assumes that #VE on a shared page is an MMIO access and tries to decode instruction to handle it. In case of load_unaligned_zeropad() it may result in confusion as it is not MMIO access. Fix it by detecting split page MMIO accesses and failing them. load_unaligned_zeropad() will recover using exception fixups. The issue was discovered by analysis and reproduced artificially. It was not triggered during testing. [ dhansen: fix up changelogs and comments for grammar and clarity, plus incorporate Kirill's off-by-one fix] Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Link: https://lkml.kernel.org/r/20220614120135.14812-4-kirill.shutemov@linux.intel.com |
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