On March 7, 2019 3:45:11 AM PST, Peter Zijlstra <pet...@infradead.org> wrote: >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(-) > > >
This is phenomenal. Thank you so much for digging into this. I'm hoping this will greatly reduce the risk of future leakage. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
