From 5d1c6c0b67c3846a6ed2804c9f6732af21a45925 Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <arnd@arndb.de>
Date: Fri, 2 Aug 2019 21:48:58 -0700
Subject: ubsan: build ubsan.c more conservatively

commit af700eaed0564d5d3963a7a51cb0843629d7fe3d upstream.

objtool points out several conditions that it does not like, depending
on the combination with other configuration options and compiler
variants:

stack protector:
  lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0xbf: call to __stack_chk_fail() with UACCESS enabled
  lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0xbe: call to __stack_chk_fail() with UACCESS enabled

stackleak plugin:
  lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0x4a: call to stackleak_track_stack() with UACCESS enabled
  lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0x4a: call to stackleak_track_stack() with UACCESS enabled

kasan:
  lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0x25: call to memcpy() with UACCESS enabled
  lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0x25: call to memcpy() with UACCESS enabled

The stackleak and kasan options just need to be disabled for this file
as we do for other files already.  For the stack protector, we already
attempt to disable it, but this fails on clang because the check is
mixed with the gcc specific -fno-conserve-stack option.  According to
Andrey Ryabinin, that option is not even needed, dropping it here fixes
the stackprotector issue.

Link: http://lkml.kernel.org/r/20190722125139.1335385-1-arnd@arndb.de
Link: https://lore.kernel.org/lkml/20190617123109.667090-1-arnd@arndb.de/t/
Link: https://lore.kernel.org/lkml/20190722091050.2188664-1-arnd@arndb.de/t/
Fixes: d08965a27e84 ("x86/uaccess, ubsan: Fix UBSAN vs. SMAP")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 lib/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'lib/Makefile')

diff --git a/lib/Makefile b/lib/Makefile
index 4bb9411fa7cf..ae2d261daec9 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -256,7 +256,8 @@ obj-$(CONFIG_UCS2_STRING) += ucs2_string.o
 obj-$(CONFIG_UBSAN) += ubsan.o
 
 UBSAN_SANITIZE_ubsan.o := n
-CFLAGS_ubsan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
+KASAN_SANITIZE_ubsan.o := n
+CFLAGS_ubsan.o := $(call cc-option, -fno-stack-protector) $(DISABLE_STACKLEAK_PLUGIN)
 
 obj-$(CONFIG_SBITMAP) += sbitmap.o
 
-- 
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