Messages in this thread Patch in this message | | | From | Nikolay Borisov <> | Subject | [PATCH 3/3] x86: Disable running 32bit processes if ia32_disabled is passed | Date | Wed, 7 Jun 2023 10:29:36 +0300 |
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In addition to disabling 32bit syscall interface let's also disable the ability to run 32bit processes altogether. This is achieved by setting the GDT_ENTRY_DEFAULT_USER32_CS descriptor to not present which would cause 32 bit processes to trap with a #NP exception. Furthermore, forbid loading compat processes as well.
Signed-off-by: Nikolay Borisov <nik.borisov@suse.com> --- arch/x86/include/asm/elf.h | 5 +++-- arch/x86/kernel/cpu/common.c | 8 ++++++++ 2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 18fd06f7936a..406245bc0fb0 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -148,9 +148,10 @@ do { \ #define elf_check_arch(x) \ ((x)->e_machine == EM_X86_64) +extern bool ia32_disabled; #define compat_elf_check_arch(x) \ - (elf_check_arch_ia32(x) || \ - (IS_ENABLED(CONFIG_X86_X32_ABI) && (x)->e_machine == EM_X86_64)) + (!ia32_disabled && (elf_check_arch_ia32(x) || \ + (IS_ENABLED(CONFIG_X86_X32_ABI) && (x)->e_machine == EM_X86_64))) static inline void elf_common_init(struct thread_struct *t, struct pt_regs *regs, const u16 ds) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 71f8b55f70c9..ddc301c09419 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2359,6 +2359,11 @@ void microcode_check(struct cpuinfo_x86 *prev_info) } #endif +static void remove_user32cs_from_gdt(void * __unused) +{ + get_current_gdt_rw()[GDT_ENTRY_DEFAULT_USER32_CS].p = 0; +} + /* * Invoked from core CPU hotplug code after hotplug operations */ @@ -2368,4 +2373,7 @@ void arch_smt_update(void) cpu_bugs_smt_update(); /* Check whether IPI broadcasting can be enabled */ apic_smt_update(); + if (ia32_disabled) + on_each_cpu(remove_user32cs_from_gdt, NULL, 1); + } -- 2.34.1
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