From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: torvalds@linux-foundation.org, tglx@linutronix.de, hpa@zytor.com,
julien.thierry@arm.com, will.deacon@arm.com, luto@amacapital.net,
mingo@kernel.org, catalin.marinas@arm.com, james.morse@arm.com,
valentin.schneider@arm.com, brgerst@gmail.com, luto@kernel.org,
bp@alien8.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org,
dvyukov@google.com, rostedt@goodmis.org
Subject: Re: [PATCH 18/20] objtool: Add UACCESS validation
Date: Fri, 8 Mar 2019 22:31:56 +0100 [thread overview]
Message-ID: <20190308213155.GD2482@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20190308210209.usq2rpedccz25va5@treble>
On Fri, Mar 08, 2019 at 03:02:09PM -0600, Josh Poimboeuf wrote:
> > +static const char *uaccess_safe_builtin[] = {
> > + /* KASAN */
>
> A short comment would be good here, something describing why a function
> might be added to the list.
There is; but I'm thinking it might be too short?
> > + "memset_orig", /* XXX why not memset_erms */
> > + "__memset",
> > + "kasan_poison_shadow",
> > + "kasan_unpoison_shadow",
> > + "__asan_poison_stack_memory",
> > + "__asan_unpoison_stack_memory",
Those are gone.
> > + "kasan_report",
That is the main kasan_report function, and is for, as the comment says:
kasan :-)
> > + "check_memory_region",
for __asan_{load,store}N
> > + /* KASAN out-of-line */
> > + "__asan_loadN_noabort",
> > + "__asan_load1_noabort",
> > + "__asan_load2_noabort",
> > + "__asan_load4_noabort",
> > + "__asan_load8_noabort",
> > + "__asan_load16_noabort",
> > + "__asan_storeN_noabort",
> > + "__asan_store1_noabort",
> > + "__asan_store2_noabort",
> > + "__asan_store4_noabort",
> > + "__asan_store8_noabort",
> > + "__asan_store16_noabort",
These, are, again as the comment suggests, the out-of-line KASAN ABI
calls.
> > + /* KASAN in-line */
> > + "__asan_report_load_n_noabort",
> > + "__asan_report_load1_noabort",
> > + "__asan_report_load2_noabort",
> > + "__asan_report_load4_noabort",
> > + "__asan_report_load8_noabort",
> > + "__asan_report_load16_noabort",
> > + "__asan_report_store_n_noabort",
> > + "__asan_report_store1_noabort",
> > + "__asan_report_store2_noabort",
> > + "__asan_report_store4_noabort",
> > + "__asan_report_store8_noabort",
> > + "__asan_report_store16_noabort",
The in-line KASAN ABI
Also, can I just say that {load,store}N vs {load,store}_n bugs the
hell out of me?
> > + /* KCOV */
> > + "write_comp_data",
the logger function
> > + "__sanitizer_cov_trace_pc",
> > + "__sanitizer_cov_trace_const_cmp1",
> > + "__sanitizer_cov_trace_const_cmp2",
> > + "__sanitizer_cov_trace_const_cmp4",
> > + "__sanitizer_cov_trace_const_cmp8",
> > + "__sanitizer_cov_trace_cmp1",
> > + "__sanitizer_cov_trace_cmp2",
> > + "__sanitizer_cov_trace_cmp4",
> > + "__sanitizer_cov_trace_cmp8",
KCOV ABI
> > + /* UBSAN */
> > + "ubsan_type_mismatch_common",
implementation
> > + "__ubsan_handle_type_mismatch",
> > + "__ubsan_handle_type_mismatch_v1",
UBSAN ABI
> > + /* misc */
> > + "csum_partial_copy_generic",
> > + "__memcpy_mcsafe",
> > + "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
> > + NULL
> > +};
> > + func = find_symbol_by_name(file->elf, *name);
>
> This won't work if the function name changes due to IPA optimizations.
> I assume these are all global functions so maybe it's fine?
With one or two exceptions, yep.
> These gotos make my head spin. Again I would much prefer a small amount
> of code duplication over this.
I didn't think the code was that bad once you see the end result, but
sure, I can try something else.
> > +++ b/tools/objtool/special.c
> > @@ -42,6 +42,7 @@
> > #define ALT_NEW_LEN_OFFSET 11
> >
> > #define X86_FEATURE_POPCNT (4*32+23)
> > +#define X86_FEATURE_SMAP (9*32+20)
> >
> > struct special_entry {
> > const char *sec;
> > @@ -107,8 +108,15 @@ static int get_alt_entry(struct elf *elf
> > * It has been requested that we don't validate the !POPCNT
> > * feature path which is a "very very small percentage of
> > * machines".
> > + *
> > + * Also, unconditionally enable SMAP; this avoids seeing paths
> > + * that pass through the STAC alternative and through the CLAC
> > + * NOPs.
>
> Why is this a problem?
'obvious' violation?
STAC; .... RET; # an AC=1 leak
.... CLAC; # spurious CLAC
If we do the STAC we must also do the CLAC. If we don't do the STAC we
must also not do the CLAC.
> > + *
> > + * XXX: We could do this for all binary NOP/single-INSN
> > + * alternatives.
>
> Same question here.
In general, validating NOPs isn't too interesting, so all NOP/INSN
binary alternatives could be forced on.
> > */
> > - if (feature == X86_FEATURE_POPCNT)
> > + if (feature == X86_FEATURE_POPCNT || feature == X86_FEATURE_SMAP)
> > alt->skip_orig = true;
> > }
I've actually changed this to depend on --uaccess, when set we force on
FEATURE_SMAP, otherwise we force off.
next prev parent reply other threads:[~2019-03-08 21:32 UTC|newest]
Thread overview: 100+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-07 11:45 [PATCH 00/20] objtool: UACCESS validation v3 Peter Zijlstra
2019-03-07 11:45 ` [PATCH 01/20] x86/ia32: Fix ia32_restore_sigcontext AC leak Peter Zijlstra
2019-03-07 11:45 ` [PATCH 02/20] i915,uaccess: Fix redundant CLAC Peter Zijlstra
2019-03-07 11:45 ` [PATCH 03/20] x86/uaccess: Move copy_user_handle_tail into asm Peter Zijlstra
2019-03-08 18:53 ` Josh Poimboeuf
2019-03-08 19:48 ` Peter Zijlstra
2019-03-08 19:53 ` Josh Poimboeuf
2019-03-10 13:22 ` Peter Zijlstra
2019-03-07 11:45 ` [PATCH 04/20] x86/uaccess: Fix up the fixup Peter Zijlstra
2019-03-07 11:45 ` [PATCH 05/20] x86/uaccess/xen: Suppress SMAP warnings Peter Zijlstra
2019-03-07 12:22 ` Juergen Gross
2019-03-07 12:32 ` Peter Zijlstra
2019-03-07 12:36 ` Juergen Gross
2019-03-08 19:00 ` Josh Poimboeuf
2019-03-08 19:03 ` Josh Poimboeuf
2019-03-10 13:19 ` Peter Zijlstra
2019-03-11 17:59 ` Josh Poimboeuf
2019-03-08 19:50 ` Peter Zijlstra
2019-03-07 11:45 ` [PATCH 06/20] x86/uaccess: Always inline user_access_begin() Peter Zijlstra
2019-03-07 11:45 ` [PATCH 07/20] x86/uaccess: Always inline force_valid_ss() Peter Zijlstra
2019-03-07 13:50 ` Peter Zijlstra
2019-03-07 18:05 ` Andy Lutomirski
2019-03-07 18:59 ` Peter Zijlstra
2019-03-07 19:06 ` Andy Lutomirski
2019-03-07 11:45 ` [PATCH 08/20] x86/uaccess: Introduce user_access_{save,restore}() Peter Zijlstra
2019-03-07 11:45 ` [PATCH 09/20] x86/uaccess,kasan: Fix KASAN vs SMAP Peter Zijlstra
2019-03-07 11:45 ` [PATCH 10/20] x86/uaccess,ubsan: Fix UBSAN " Peter Zijlstra
2019-03-07 11:45 ` [PATCH 11/20] x86/uaccess,ftrace: Fix ftrace_likely_update() " Peter Zijlstra
2019-03-07 11:45 ` [PATCH 12/20] objtool: Set insn->func for alternatives Peter Zijlstra
2019-03-08 19:16 ` Josh Poimboeuf
2019-03-08 19:51 ` Peter Zijlstra
2019-03-07 11:45 ` [PATCH 13/20] objtool: Hande function aliases Peter Zijlstra
2019-03-08 19:23 ` Josh Poimboeuf
2019-03-08 19:52 ` Peter Zijlstra
2019-03-08 20:00 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 14/20] objtool: Rewrite add_ignores() Peter Zijlstra
2019-03-08 19:29 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 15/20] objtool: Add --backtrace support Peter Zijlstra
2019-03-08 19:33 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 16/20] objtool: Rewrite alt->skip_orig Peter Zijlstra
2019-03-08 20:15 ` Josh Poimboeuf
2019-03-08 21:34 ` Peter Zijlstra
2019-03-08 22:27 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 17/20] objtool: Fix sibling call detection Peter Zijlstra
2019-03-08 20:22 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 18/20] objtool: Add UACCESS validation Peter Zijlstra
2019-03-07 16:33 ` Linus Torvalds
2019-03-07 17:10 ` hpa
2019-03-07 17:41 ` Peter Zijlstra
2019-03-07 17:54 ` Linus Torvalds
2019-03-07 18:48 ` Peter Zijlstra
2019-03-07 18:51 ` hpa
2019-03-07 19:03 ` Peter Zijlstra
2019-03-08 15:01 ` Josh Poimboeuf
2019-03-08 15:07 ` Peter Zijlstra
2019-03-07 20:23 ` Peter Zijlstra
2019-03-07 20:40 ` Peter Zijlstra
2019-03-08 15:07 ` Josh Poimboeuf
2019-03-08 15:23 ` Peter Zijlstra
2019-03-07 20:15 ` Andrey Ryabinin
2019-03-07 20:33 ` Peter Zijlstra
2019-03-07 20:40 ` Andrey Ryabinin
2019-03-07 20:42 ` Peter Zijlstra
2019-03-08 21:02 ` Josh Poimboeuf
2019-03-08 21:31 ` Peter Zijlstra [this message]
2019-03-08 21:54 ` Josh Poimboeuf
2019-03-10 13:10 ` Peter Zijlstra
2019-03-11 18:01 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 19/20] objtool: uaccess PUSHF/POPF support Peter Zijlstra
2019-03-08 21:11 ` Josh Poimboeuf
2019-03-10 13:12 ` Peter Zijlstra
2019-03-07 11:45 ` [PATCH 20/20] objtool: Add Direction Flag validation Peter Zijlstra
2019-03-08 21:16 ` Josh Poimboeuf
2019-03-08 21:33 ` Peter Zijlstra
2019-03-08 21:56 ` Josh Poimboeuf
2019-03-10 13:13 ` Peter Zijlstra
2019-03-11 18:00 ` Josh Poimboeuf
2019-03-07 12:03 ` [PATCH 00/20] objtool: UACCESS validation v3 Peter Zijlstra
2019-03-07 12:55 ` Peter Zijlstra
2019-03-07 13:13 ` Peter Zijlstra
2019-03-07 16:47 ` Josh Poimboeuf
2019-03-07 16:50 ` Josh Poimboeuf
2019-03-07 17:00 ` Linus Torvalds
2019-03-07 17:17 ` Josh Poimboeuf
2019-03-07 17:38 ` Peter Zijlstra
2019-03-07 17:45 ` Linus Torvalds
2019-03-07 18:18 ` Steven Rostedt
2019-03-10 13:16 ` Peter Zijlstra
2019-04-19 10:08 ` [PATCH] compiler.h, tracing: Remove CONFIG_PROFILE_ALL_BRANCHES Ingo Molnar
2019-04-19 13:04 ` Steven Rostedt
2019-03-07 17:04 ` [PATCH 00/20] objtool: UACCESS validation v3 hpa
2019-03-07 17:18 ` Josh Poimboeuf
2019-03-07 17:29 ` hpa
2019-03-07 17:45 ` Josh Poimboeuf
2019-03-07 17:48 ` Linus Torvalds
2019-03-07 17:43 ` Peter Zijlstra
2019-03-07 17:48 ` Josh Poimboeuf
2019-04-03 8:21 ` [tip:core/objtool] tracing: Improve "if" macro code generation tip-bot for Josh Poimboeuf
2019-03-07 16:31 ` [PATCH 00/20] objtool: UACCESS validation v3 Linus Torvalds
2019-03-07 17:14 ` hpa
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