diff options
| author | Rick Edgecombe <rick.p.edgecombe@intel.com> | 2023-06-12 17:10:44 -0700 |
|---|---|---|
| committer | Rick Edgecombe <rick.p.edgecombe@intel.com> | 2023-07-11 14:12:19 -0700 |
| commit | ae1f05a617dcbc0a732fbeba0893786cd009536c (patch) | |
| tree | 7bc96e4ab50af87de9dda602be0535a526b917c0 | |
| parent | e5136e876581ba5b63220378e25fec9dcec7bad1 (diff) | |
x86/mm: Warn if create Write=0,Dirty=1 with raw prot
When user shadow stack is in use, Write=0,Dirty=1 is treated by the CPU as
shadow stack memory. So for shadow stack memory this bit combination is
valid, but when Dirty=1,Write=1 (conventionally writable) memory is being
write protected, the kernel has been taught to transition the Dirty=1
bit to SavedDirty=1, to avoid inadvertently creating shadow stack
memory. It does this inside pte_wrprotect() because it knows the PTE is
not intended to be a writable shadow stack entry, it is supposed to be
write protected.
However, when a PTE is created by a raw prot using mk_pte(), mk_pte()
can't know whether to adjust Dirty=1 to SavedDirty=1. It can't
distinguish between the caller intending to create a shadow stack PTE or
needing the SavedDirty shift.
The kernel has been updated to not do this, and so Write=0,Dirty=1
memory should only be created by the pte_mkfoo() helpers. Add a warning
to make sure no new mk_pte() start doing this, like, for example,
set_memory_rox() did.
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Tested-by: Pengfei Xu <pengfei.xu@intel.com>
Tested-by: John Allen <john.allen@amd.com>
Tested-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/all/20230613001108.3040476-19-rick.p.edgecombe%40intel.com
| -rw-r--r-- | arch/x86/include/asm/pgtable.h | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 9255b5b7a9d9..61b52445e4d6 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1033,7 +1033,14 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd) * (Currently stuck as a macro because of indirect forward reference * to linux/mm.h:page_to_nid()) */ -#define mk_pte(page, pgprot) pfn_pte(page_to_pfn(page), (pgprot)) +#define mk_pte(page, pgprot) \ +({ \ + pgprot_t __pgprot = pgprot; \ + \ + WARN_ON_ONCE((pgprot_val(__pgprot) & (_PAGE_DIRTY | _PAGE_RW)) == \ + _PAGE_DIRTY); \ + pfn_pte(page_to_pfn(page), __pgprot); \ +}) static inline int pmd_bad(pmd_t pmd) { |