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x86/mm: Refuse W^X violations

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x86 has STRICT_*_RWX, but not even a warning when someone violates it.

Add this warning and fully refuse the transition.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/YwySW3ROc21hN7g9@hirez.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra 2022-08-29 12:18:03 +02:00 committed by Dave Hansen
parent 86af8230ce
commit 652c5bf380
1 changed files with 32 additions and 0 deletions
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32
arch/x86/mm/pat/set_memory.c
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@ -579,6 +579,33 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long start,
return __pgprot(pgprot_val(prot) & ~forbidden);
}
/*
* Validate and enforce strict W^X semantics.
*/
static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long start,
unsigned long pfn, unsigned long npg)
{
unsigned long end;
if (!cpu_feature_enabled(X86_FEATURE_NX))
return new;
if (!((pgprot_val(old) ^ pgprot_val(new)) & (_PAGE_RW | _PAGE_NX)))
return new;
if ((pgprot_val(new) & (_PAGE_RW | _PAGE_NX)) != _PAGE_RW)
return new;
end = start + npg * PAGE_SIZE - 1;
WARN_ONCE(1, "CPA refuse W^X violation: %016llx -> %016llx range: 0x%016lx - 0x%016lx PFN %lx\n",
(unsigned long long)pgprot_val(old),
(unsigned long long)pgprot_val(new),
start, end, pfn);
/* refuse the transition into WX */
return old;
}
/*
* Lookup the page table entry for a virtual address in a specific pgd.
* Return a pointer to the entry and the level of the mapping.
@ -885,6 +912,8 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address,
new_prot = static_protections(req_prot, lpaddr, old_pfn, numpages,
psize, CPA_DETECT);
new_prot = verify_rwx(old_prot, new_prot, lpaddr, old_pfn, numpages);
/*
* If there is a conflict, split the large page.
*
@ -1525,6 +1554,7 @@ repeat:
if (level == PG_LEVEL_4K) {
pte_t new_pte;
pgprot_t old_prot = pte_pgprot(old_pte);
pgprot_t new_prot = pte_pgprot(old_pte);
unsigned long pfn = pte_pfn(old_pte);
@ -1536,6 +1566,8 @@ repeat:
new_prot = static_protections(new_prot, address, pfn, 1, 0,
CPA_PROTECT);
new_prot = verify_rwx(old_prot, new_prot, address, pfn, 1);
new_prot = pgprot_clear_protnone_bits(new_prot);
/*