Messages in this thread Patch in this message | | | Date | Tue, 15 Dec 2015 09:45:40 -0800 | Subject | Re: 4.4-rc5: ugly warn on: 5 W+X pages found | From | Linus Torvalds <> |
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On Tue, Dec 15, 2015 at 1:40 AM, Pavel Machek <pavel@ucw.cz> wrote: > > I tried applying: > > [PATCH 1/2] x86_32/mm: Set NX in __supported_pte_mask before enabling > paging > > but I still get > > [ 2.691897] x86/mm: Found insecure W+X mapping at address ffe69000/0xffe69000
This may be an insane suggestion, but how about we try to detect when that entry gets set, rather than after the fact.
Something really brute-force like
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 6ec0c8b2e9df..538c9bb239b9 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -337,6 +337,13 @@ static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd)
#endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */
+static inline int kernel_write_execute_prot(pgprotval_t protval) +{ + return !(protval & _PAGE_USER) && + !(protval & _PAGE_NX) && + (protval & _PAGE_RW); +} + /* * Mask out unsupported bits in a present pgprot. Non-present pgprots * can use those bits for other purposes, so leave them be. @@ -345,8 +352,10 @@ static inline pgprotval_t massage_pgprot(pgprot_t pgprot) { pgprotval_t protval = pgprot_val(pgprot);
- if (protval & _PAGE_PRESENT) + if (protval & _PAGE_PRESENT) { protval &= __supported_pte_mask; + WARN_ON_ONCE(kernel_write_execute_prot(protval)); + } return protval; } or similar?
The above is entirely untested. Maybe it doesn't compile. Or boot. Or work.
Linus
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