Messages in this thread | | | Date | Thu, 28 Feb 2019 15:54:50 +0100 | From | Peter Zijlstra <> | Subject | [PATCH 0/8] objtool: UACCESS validation v2 |
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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 an annotation to mark (a very limited) set of functions as UACCESS-safe (eg. the planned: unsafe_copy_{to,from}_user()).
This set now compiles x86_64-allmodconfig _almost_ clean:
arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0x30: redundant UACCESS disable drivers/xen/privcmd.o: warning: objtool: privcmd_ioctl()+0x1c0: call to {dynamic}() with UACCESS enabled drivers/xen/privcmd.o: warning: objtool: privcmd_ioctl()+0x8f8: call to hypercall_page() with UACCESS enabled
Also; I found the UACCESS_SAFE() annotation as presented in these patches to be inadequate; so I might go back to the STH_STRTAB variant for this. Alternatively, we can simply keep the hard-coded list we have now. There really should not be many more function on there.
*compile tested only*, esp. the KASAN changes have not been verified to actually *work*.
--- arch/x86/ia32/ia32_signal.c | 29 +++-- arch/x86/include/asm/bug.h | 28 ++-- arch/x86/include/asm/kasan.h | 15 +++ drivers/gpu/drm/i915/i915_gem_execbuffer.c | 3 +- include/asm-generic/bug.h | 1 + include/linux/frame.h | 23 ++++ include/linux/kasan.h | 12 +- lib/bug.c | 9 +- mm/kasan/generic.c | 4 +- mm/kasan/kasan.h | 2 +- mm/kasan/report.c | 2 +- tools/objtool/arch.h | 6 +- tools/objtool/arch/x86/decode.c | 22 +++- tools/objtool/check.c | 197 +++++++++++++++++++++++------ tools/objtool/check.h | 3 +- tools/objtool/elf.c | 15 ++- tools/objtool/elf.h | 3 +- 17 files changed, 290 insertions(+), 84 deletions(-)
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