linux-kernel - [tip:x86/urgent] x86/mm/mem_encrypt: Disable all instrumentation for early SME setup

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Date:   Tue, 30 Apr 2019 09:04:15 -0700
From:   tip-bot for Gary Hook <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     bigeasy@...utronix.de, andriy.shevchenko@...ux.intel.com,
        tglx@...utronix.de, kent.overstreet@...il.com,
        dave.hansen@...ux.intel.com, peterz@...radead.org,
        lirongqing@...du.com, bp@...e.de, colyli@...e.de, mingo@...hat.com,
        bbrezillon@...nel.org, Gary.Hook@....com, luto@...nel.org,
        akpm@...ux-foundation.org, willy@...radead.org, gary.hook@....com,
        mingo@...nel.org, keescook@...omium.org,
        alexander.shishkin@...ux.intel.com, yamada.masahiro@...ionext.com,
        hpa@...or.com, linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [tip:x86/urgent] x86/mm/mem_encrypt: Disable all instrumentation
 for early SME setup

Commit-ID:  b51ce3744f115850166f3d6c292b9c8cb849ad4f
Gitweb:     https://git.kernel.org/tip/b51ce3744f115850166f3d6c292b9c8cb849ad4f
Author:     Gary Hook <Gary.Hook@....com>
AuthorDate: Mon, 29 Apr 2019 22:22:58 +0000
Committer:  Borislav Petkov <bp@...e.de>
CommitDate: Tue, 30 Apr 2019 17:59:08 +0200

x86/mm/mem_encrypt: Disable all instrumentation for early SME setup

Enablement of AMD's Secure Memory Encryption feature is determined very
early after start_kernel() is entered. Part of this procedure involves
scanning the command line for the parameter 'mem_encrypt'.

To determine intended state, the function sme_enable() uses library
functions cmdline_find_option() and strncmp(). Their use occurs early
enough such that it cannot be assumed that any instrumentation subsystem
is initialized.

For example, making calls to a KASAN-instrumented function before KASAN
is set up will result in the use of uninitialized memory and a boot
failure.

When AMD's SME support is enabled, conditionally disable instrumentation
of these dependent functions in lib/string.c and arch/x86/lib/cmdline.c.

 [ bp: Get rid of intermediary nostackp var and cleanup whitespace. ]

Fixes: aca20d546214 ("x86/mm: Add support to make use of Secure Memory Encryption")
Reported-by: Li RongQing <lirongqing@...du.com>
Signed-off-by: Gary R Hook <gary.hook@....com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Boris Brezillon <bbrezillon@...nel.org>
Cc: Coly Li <colyli@...e.de>
Cc: "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Kent Overstreet <kent.overstreet@...il.com>
Cc: "luto@...nel.org" <luto@...nel.org>
Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: "mingo@...hat.com" <mingo@...hat.com>
Cc: "peterz@...radead.org" <peterz@...radead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: x86-ml <x86@...nel.org>
Link: https://lkml.kernel.org/r/155657657552.7116.18363762932464011367.stgit@sosrh3.amd.com
---
 arch/x86/lib/Makefile | 12 ++++++++++++
 lib/Makefile          | 11 +++++++++++
 2 files changed, 23 insertions(+)

diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 140e61843a07..3cb3af51ec89 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -6,6 +6,18 @@
 # Produces uninteresting flaky coverage.
 KCOV_INSTRUMENT_delay.o	:= n
 
+# Early boot use of cmdline; don't instrument it
+ifdef CONFIG_AMD_MEM_ENCRYPT
+KCOV_INSTRUMENT_cmdline.o := n
+KASAN_SANITIZE_cmdline.o  := n
+
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_cmdline.o = -pg
+endif
+
+CFLAGS_cmdline.o := $(call cc-option, -fno-stack-protector)
+endif
+
 inat_tables_script = $(srctree)/arch/x86/tools/gen-insn-attr-x86.awk
 inat_tables_maps = $(srctree)/arch/x86/lib/x86-opcode-map.txt
 quiet_cmd_inat_tables = GEN     $@
diff --git a/lib/Makefile b/lib/Makefile
index 3b08673e8881..18c2be516ab4 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -17,6 +17,17 @@ KCOV_INSTRUMENT_list_debug.o := n
 KCOV_INSTRUMENT_debugobjects.o := n
 KCOV_INSTRUMENT_dynamic_debug.o := n
 
+# Early boot use of cmdline, don't instrument it
+ifdef CONFIG_AMD_MEM_ENCRYPT
+KASAN_SANITIZE_string.o := n
+
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_string.o = -pg
+endif
+
+CFLAGS_string.o := $(call cc-option, -fno-stack-protector)
+endif
+
 lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 rbtree.o radix-tree.o timerqueue.o xarray.o \
 	 idr.o int_sqrt.o extable.o \