diff options
| author | Dave Hansen <[email protected]> | 2022-10-03 13:23:46 -0700 |
|---|---|---|
| committer | Dave Hansen <[email protected]> | 2022-10-04 12:53:52 -0700 |
| commit | c5129ecc12a3101555d8922b1e0aa90f91247ab6 (patch) | |
| tree | e34c856f6309202ccb083abd7c24bdd7d147dc58 | |
| parent | 8c4934f4754057e3577bb1536c6ecc0efa2c966e (diff) | |
x86/mm: Ease W^X enforcement back to just a warning
Currently, the "change_page_attr" (CPA) code refuses to create
W+X mappings on 64-bit kernels. There have been reports both
from 32-bit[1] and from BPF[2] users where this change kept the
system from booting.
These reports are showing up even after about a month of soak
time in -next.
To avoid breaking anything, never enforce W^X. Always warn
and return the requested permissions even if a problem is
detected.
1. https://lore.kernel.org/all/CAMj1kXHcF_iK_g0OZSkSv56Wmr=eQGQwNstcNjLEfS=mm7a06w@mail.gmail.com/
2. https://lore.kernel.org/bpf/[email protected]/T/#u
Signed-off-by: Dave Hansen <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: [email protected]
Cc: "H. Peter Anvin" <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Peter Zijlstra <[email protected]>
| -rw-r--r-- | arch/x86/mm/pat/set_memory.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index efe882c753ca..97342c42dda8 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -580,7 +580,7 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long start, } /* - * Validate and enforce strict W^X semantics. + * Validate 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) @@ -595,7 +595,7 @@ static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long star if (IS_ENABLED(CONFIG_X86_32)) return new; - /* Only enforce when NX is supported: */ + /* Only verify when NX is supported: */ if (!(__supported_pte_mask & _PAGE_NX)) return new; @@ -606,13 +606,17 @@ static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long star 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", + WARN_ONCE(1, "CPA detected 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; + /* + * For now, allow all permission change attempts by returning the + * attempted permissions. This can 'return old' to actively + * refuse the permission change at a later time. + */ + return new; } /* |