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Message-ID: <3D9DB587-A502-42EA-A6F6-5790735310F5@zytor.com>
Date: Mon, 06 May 2019 00:24:32 -0700
From: hpa@...or.com
To: Ingo Molnar <mingo@...nel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
CC: linux-kernel@...r.kernel.org,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>,
Andy Lutomirski <luto@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] objtool changes for v5.2: Add build-time uaccess permissions and DF validation
On May 6, 2019 12:20:12 AM PDT, Ingo Molnar <mingo@...nel.org> wrote:
>Linus,
>
>Please pull the latest core-objtool-for-linus git tree from:
>
>git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
>core-objtool-for-linus
>
># HEAD: 29da93fea3ea39ab9b12270cc6be1b70ef201c9e mm/uaccess: Use
>'unsigned long' to placate UBSAN warnings on older GCC versions
>
>This is a series from Peter Zijlstra that adds x86 build-time uaccess
>validation of SMAP to objtool, which will detect and warn about the
>following uaccess API usage bugs and weirdnesses:
>
> call to %s() with UACCESS enabled
> return with UACCESS enabled
> return with UACCESS disabled from a UACCESS-safe function
> recursive UACCESS enable
> redundant UACCESS disable
> UACCESS-safe disables UACCESS
>
>As it turns out not leaking uaccess permissions outside the intended
>uaccess functionality is hard when the interfaces are complex and when
>such bugs are mostly dormant.
>
>As a bonus we now also check the DF flag. We had at least one
>high-profile bug in that area in the early days of Linux, and the
>checking is fairly simple. The checks performed and warnings emitted
>are:
>
> call to %s() with DF set
> return with DF set
> return with modified stack frame
> recursive STD
> redundant CLD
>
>It's all x86-only for now, but later on this can also be used for PAN
>on
>ARM and objtool is fairly cross-platform in principle.
>
>While all warnings emitted by this new checking facility that got
>reported to us were fixed, there might be GCC version dependent
>warnings
>that were not reported yet - which we'll address, should they trigger.
>
>The warnings are non-fatal build warnings.
>
> Thanks,
>
> Ingo
>
>------------------>
>Josh Poimboeuf (1):
> tracing: Improve "if" macro code generation
>
>Peter Zijlstra (26):
> sched/x86: Save [ER]FLAGS on context switch
> x86/ia32: Fix ia32_restore_sigcontext() AC leak
> i915, uaccess: Fix redundant CLAC
> x86/uaccess: Move copy_user_handle_tail() into asm
> x86/uaccess: Fix up the fixup
> x86/nospec, objtool: Introduce ANNOTATE_IGNORE_ALTERNATIVE
> x86/uaccess, xen: Suppress SMAP warnings
> x86/uaccess: Always inline user_access_begin()
> x86/uaccess, signal: Fix AC=1 bloat
> x86/uaccess: Introduce user_access_{save,restore}()
> x86/smap: Ditch __stringify()
> x86/uaccess, kasan: Fix KASAN vs SMAP
> x86/uaccess, ubsan: Fix UBSAN vs. SMAP
> x86/uaccess, ftrace: Fix ftrace_likely_update() vs. SMAP
> x86/uaccess, kcov: Disable stack protector
> objtool: Set insn->func for alternatives
> objtool: Handle function aliases
> objtool: Rewrite add_ignores()
> objtool: Add --backtrace support
> objtool: Rewrite alt->skip_orig
> objtool: Fix sibling call detection
> objtool: Add UACCESS validation
> objtool: Add Direction Flag validation
> sched/x86_64: Don't save flags on context switch
>x86/uaccess: Dont leak the AC flag into __put_user() argument
>evaluation
>mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC
>versions
>
>
> arch/x86/entry/entry_32.S | 2 +
> arch/x86/ia32/ia32_signal.c | 29 ++-
> arch/x86/include/asm/alternative-asm.h | 11 +
> arch/x86/include/asm/alternative.h | 10 +
> arch/x86/include/asm/asm.h | 24 --
> arch/x86/include/asm/nospec-branch.h | 28 +-
> arch/x86/include/asm/smap.h | 37 ++-
> arch/x86/include/asm/switch_to.h | 1 +
> arch/x86/include/asm/uaccess.h | 12 +-
> arch/x86/include/asm/uaccess_64.h | 3 -
> arch/x86/include/asm/xen/hypercall.h | 24 +-
> arch/x86/kernel/process_32.c | 7 +
> arch/x86/kernel/process_64.c | 1 +
> arch/x86/kernel/signal.c | 29 ++-
> 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/compiler.h | 2 +-
> include/linux/uaccess.h | 2 +
> kernel/Makefile | 1 +
> kernel/trace/trace_branch.c | 4 +
> lib/Makefile | 1 +
> lib/strncpy_from_user.c | 5 +-
> lib/strnlen_user.c | 4 +-
> lib/ubsan.c | 4 +
> mm/kasan/Makefile | 3 +
> mm/kasan/common.c | 10 +
> mm/kasan/report.c | 3 +-
> scripts/Makefile.build | 3 +
> tools/objtool/arch.h | 8 +-
> tools/objtool/arch/x86/decode.c | 21 +-
> tools/objtool/builtin-check.c | 4 +-
> tools/objtool/builtin.h | 2 +-
>tools/objtool/check.c | 400
>++++++++++++++++++++++-------
> tools/objtool/check.h | 4 +-
> tools/objtool/elf.c | 15 +-
> tools/objtool/elf.h | 3 +-
> tools/objtool/special.c | 18 ++
> tools/objtool/special.h | 1 +
> tools/objtool/warn.h | 8 +
> 41 files changed, 602 insertions(+), 219 deletions(-)
Superb work.
--
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