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| author | Dave Hansen <dave.hansen@linux.intel.com> | 2022-09-24 00:29:45 +0300 |
|---|---|---|
| committer | Dave Hansen <dave.hansen@linux.intel.com> | 2022-10-03 23:12:23 +0300 |
| commit | 8c4934f4754057e3577bb1536c6ecc0efa2c966e (patch) | |
| tree | 82c2afe994803355b0ac3a0dad7df44f880779b9 | |
| parent | 334b2cea811944df99ae2172bcc0effcdfdbe862 (diff) | |
| download | linux-8c4934f4754057e3577bb1536c6ecc0efa2c966e.tar.xz | |
x86/mm: Disable W^X detection and enforcement on 32-bit
The 32-bit code is in a weird spot. Some 32-bit builds (non-PAE) do not
even have NX support. Even PAE builds that support NX have to contend
with things like EFI data and code mixed in the same pages where W+X
is unavoidable.
The folks still running X86_32=y kernels are unlikely to care much about
NX. That combined with the fundamental inability fix _all_ of the W+X
things means this code had little value on X86_32=y. Disable the checks.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Andy Shevchenko <andy@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: linux-efi@vger.kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/all/CAMj1kXHcF_iK_g0OZSkSv56Wmr=eQGQwNstcNjLEfS=mm7a06w@mail.gmail.com/
| -rw-r--r-- | arch/x86/mm/pat/set_memory.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index 20b1e24baa85..efe882c753ca 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -587,6 +587,14 @@ static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long star { unsigned long end; + /* + * 32-bit has some unfixable W+X issues, like EFI code + * and writeable data being in the same page. Disable + * detection and enforcement there. + */ + if (IS_ENABLED(CONFIG_X86_32)) + return new; + /* Only enforce when NX is supported: */ if (!(__supported_pte_mask & _PAGE_NX)) return new; |