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x86/mm: Ensure input to pfn_to_kaddr() is treated as a 64-bit type

Steve Best requested to merge sfbest/centos-stream-9:36906 into main

JIRA: https://issues.redhat.com/browse/RHEL-36906
CVE: CVE-2023-52659

Build Info: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=61450304
Tested: Did sanity boot testing Intel (intel-arrowlake-s-02) system.

commit 8e5647a723c49d73b9f108a8bb38e8c29d3948ea
Author: Michael Roth michael.roth@amd.com
Date: Wed Nov 22 10:37:00 2023 -0600

x86/mm: Ensure input to pfn_to_kaddr() is treated as a 64-bit type  

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 an inline function,  
instead of a 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 ARM explicitly casting the input to phys_addr_t:  

  e48866647b48 ("ARM: 8396/1: use phys_addr_t in pfn_to_kaddr()")  

A C inline function is even better though.  

[ mingo: Refined the changelog some more & added __always_inline. ]  

Fixes: 6c3211796326 ("x86/sev: Add SNP-specific unaccepted memory support")  
Suggested-by: Dave Hansen <dave.hansen@intel.com>  
Suggested-by: H. Peter Anvin <hpa@zytor.com>  
Signed-off-by: Michael Roth <michael.roth@amd.com>  
Signed-off-by: Ingo Molnar <mingo@kernel.org>  
Link: https://lore.kernel.org/r/20231122163700.400507-1-michael.roth@amd.com  
Cc: Andy Lutomirski <luto@kernel.org>  
Cc: Peter Zijlstra <peterz@infradead.org>  
Cc: Rik van Riel <riel@surriel.com>  
Cc: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: Steve Best sbest@redhat.com

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