Messages in this thread Patch in this message | | | From | Michael Roth <> | Subject | [PATCH v3] x86: Ensure input to pfn_to_kaddr() is treated as a 64-bit type | Date | Wed, 22 Nov 2023 10:37:00 -0600 |
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On 64-bit platforms, the pfn_to_kaddr() macro requires that the input value is 64-bits in order to ensure that valid address bits don't get lost when shifting that input by PAGE_SHIFT to calculate the physical address to provide a virtual address for.
One such example is in pvalidate_pages() (used by SEV-SNP guests), where the GFN in the struct used for page-state change requests is a 40-bit bit-field, so attempts to pass this GFN field directly into pfn_to_kaddr() ends up causing guest crashes when dealing with addresses above the 1TB range due to the above.
Fix this issue with SEV-SNP guests, as well as any similar cases that might cause issues in current/future code, by using a inline function, instead of the macro, so that the input is implicitly cast to the expected 64-bit input type prior to performing the shift operation.
While it might be argued that the issue is on the caller side, other archs/macros have taken similar approaches to deal with instances like this, such as commit e48866647b48 ("ARM: 8396/1: use phys_addr_t in pfn_to_kaddr()").
Suggested-by: Dave Hansen <dave.hansen@intel.com> Suggested-by: H. Peter Anvin <hpa@zytor.com> Fixes: 6c3211796326 ("x86/sev: Add SNP-specific unaccepted memory support") Signed-off-by: Michael Roth <michael.roth@amd.com> --- v3: - Use an inline function instead of a macro to handle the cast (Peter) v2: - Move the cast down into pfn_to_kaddr() to fix other possible instances (Dave) - Rename from "x86/sev: Fix overflow when computing address for PVALIDATE"
arch/x86/include/asm/page.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h index d18e5c332cb9..aa8930da42fd 100644 --- a/arch/x86/include/asm/page.h +++ b/arch/x86/include/asm/page.h @@ -66,10 +66,14 @@ static inline void copy_user_page(void *to, void *from, unsigned long vaddr, * virt_addr_valid(kaddr) returns true. */ #define virt_to_page(kaddr) pfn_to_page(__pa(kaddr) >> PAGE_SHIFT) -#define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT) extern bool __virt_addr_valid(unsigned long kaddr); #define virt_addr_valid(kaddr) __virt_addr_valid((unsigned long) (kaddr)) +static inline void *pfn_to_kaddr(unsigned long pfn) +{ + return __va(pfn << PAGE_SHIFT); +} + static __always_inline u64 __canonical_address(u64 vaddr, u8 vaddr_bits) { return ((s64)vaddr << (64 - vaddr_bits)) >> (64 - vaddr_bits); -- 2.25.1
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