[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <169780183325.3135.17534481806232148373.tip-bot2@tip-bot2>
Date: Fri, 20 Oct 2023 11:37:13 -0000
From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Nathan Chancellor <nathan@...nel.org>,
Josh Poimboeuf <jpoimboe@...nel.org>,
"Borislav Petkov (AMD)" <bp@...en8.de>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Marco Elver <elver@...gle.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/bugs] x86/retpoline: Make sure there are no unconverted
return thunks due to KCSAN
The following commit has been merged into the x86/bugs branch of tip:
Commit-ID: 2d7ce49f58dc95495b3e22e45d2be7de909b2c63
Gitweb: https://git.kernel.org/tip/2d7ce49f58dc95495b3e22e45d2be7de909b2c63
Author: Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate: Tue, 17 Oct 2023 09:59:46 -07:00
Committer: Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Fri, 20 Oct 2023 13:02:23 +02:00
x86/retpoline: Make sure there are no unconverted return thunks due to KCSAN
Enabling CONFIG_KCSAN leads to unconverted, default return thunks to
remain after patching.
As David Kaplan describes in his debugging of the issue, it is caused by
a couple of KCSAN-generated constructors which aren't processed by
objtool:
"When KCSAN is enabled, GCC generates lots of constructor functions
named _sub_I_00099_0 which call __tsan_init and then return. The
returns in these are generally annotated normally by objtool and fixed
up at runtime. But objtool runs on vmlinux.o and vmlinux.o does not
include a couple of object files that are in vmlinux, like
init/version-timestamp.o and .vmlinux.export.o, both of which contain
_sub_I_00099_0 functions. As a result, the returns in these functions
are not annotated, and the panic occurs when we call one of them in
do_ctors and it uses the default return thunk.
This difference can be seen by counting the number of these functions in the object files:
$ objdump -d vmlinux.o|grep -c "<_sub_I_00099_0>:"
2601
$ objdump -d vmlinux|grep -c "<_sub_I_00099_0>:"
2603
If these functions are only run during kernel boot, there is no
speculation concern."
Fix it by disabling KCSAN on version-timestamp.o and .vmlinux.export.o
so the extra functions don't get generated. KASAN and GCOV are already
disabled for those files.
[ bp: Massage commit message. ]
Closes: https://lore.kernel.org/lkml/20231016214810.GA3942238@dev-arch.thelio-3990X/
Reported-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Acked-by: Marco Elver <elver@...gle.com>
Tested-by: Nathan Chancellor <nathan@...nel.org>
Link: https://lore.kernel.org/r/20231017165946.v4i2d4exyqwqq3bx@treble
---
init/Makefile | 1 +
scripts/Makefile.vmlinux | 1 +
2 files changed, 2 insertions(+)
diff --git a/init/Makefile b/init/Makefile
index ec557ad..cbac576 100644
--- a/init/Makefile
+++ b/init/Makefile
@@ -60,4 +60,5 @@ include/generated/utsversion.h: FORCE
$(obj)/version-timestamp.o: include/generated/utsversion.h
CFLAGS_version-timestamp.o := -include include/generated/utsversion.h
KASAN_SANITIZE_version-timestamp.o := n
+KCSAN_SANITIZE_version-timestamp.o := n
GCOV_PROFILE_version-timestamp.o := n
diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
index 3cd6ca1..c9f3e03 100644
--- a/scripts/Makefile.vmlinux
+++ b/scripts/Makefile.vmlinux
@@ -19,6 +19,7 @@ quiet_cmd_cc_o_c = CC $@
ifdef CONFIG_MODULES
KASAN_SANITIZE_.vmlinux.export.o := n
+KCSAN_SANITIZE_.vmlinux.export.o := n
GCOV_PROFILE_.vmlinux.export.o := n
targets += .vmlinux.export.o
vmlinux: .vmlinux.export.o
Powered by blists - more mailing lists