Teach objtool to validate the UACCESS (SMAP, PAN) rules with are currently unenforced and (therefore obviously) violated.
UACCESS sections should be small; we want to limit the amount of code that can touch userspace. Furthermore, UACCESS state isn't scheduled, this means that anything that directly calls into the scheduler will result in random code running with UACCESS enabled and possibly getting back into the UACCESS region with UACCESS disabled and causing faults. Forbid any CALL/RET while UACCESS is enabled; but provide a few exceptions. This builds x86_64-allmodconfig clean, and I've only got a few randconfig failures left (GCC-8) that I'm not quite understanding. --- arch/x86/ia32/ia32_signal.c | 29 ++- arch/x86/include/asm/asm.h | 24 -- arch/x86/include/asm/nospec-branch.h | 4 +- arch/x86/include/asm/smap.h | 20 ++ arch/x86/include/asm/uaccess.h | 5 +- arch/x86/include/asm/uaccess_64.h | 3 - arch/x86/include/asm/xen/hypercall.h | 26 +- arch/x86/kernel/signal.c | 2 +- arch/x86/lib/copy_user_64.S | 48 ++++ arch/x86/lib/memcpy_64.S | 3 +- arch/x86/lib/usercopy_64.c | 20 -- drivers/gpu/drm/i915/i915_gem_execbuffer.c | 6 +- include/linux/uaccess.h | 2 + kernel/trace/trace_branch.c | 4 + lib/Makefile | 1 + lib/ubsan.c | 4 + mm/kasan/Makefile | 3 + mm/kasan/common.c | 10 + mm/kasan/report.c | 3 +- scripts/Makefile.build | 3 + tools/objtool/Makefile | 2 +- tools/objtool/arch.h | 8 +- tools/objtool/arch/x86/decode.c | 26 +- tools/objtool/builtin-check.c | 4 +- tools/objtool/builtin.h | 2 +- tools/objtool/check.c | 382 ++++++++++++++++++++++------- tools/objtool/check.h | 4 +- tools/objtool/elf.c | 15 +- tools/objtool/elf.h | 3 +- tools/objtool/special.c | 10 +- tools/objtool/warn.h | 8 + 31 files changed, 511 insertions(+), 173 deletions(-)
