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@xxxxxxxxxxxx> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx> Cc: Darren Hart <dvhart@xxxxxxxxxxxxx> Cc: Andy Shevchenko <andy@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: x86@xxxxxxxxxx Cc: linux-efi@xxxxxxxxxxxxxxx Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Link: https://lore.kernel.org/all/CAMj1kXHcF_iK_g0OZSkSv56Wmr=eQGQwNstcNjLEfS=mm7a06w@xxxxxxxxxxxxxx/ --- arch/x86/mm/pat/set_memory.c | 8 ++++++++ 1 file changed, 8 insertions(+) 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; -- 2.34.1
