From: Josh Poimboeuf <jpoimboe@kernel.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: "Kaplan, David" <David.Kaplan@amd.com>,
Borislav Petkov <bp@alien8.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-tip-commits@vger.kernel.org"
<linux-tip-commits@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
"x86@kernel.org" <x86@kernel.org>,
"llvm@lists.linux.dev" <llvm@lists.linux.dev>
Subject: [PATCH] x86/srso: Fix panic in return thunk during boot
Date: Tue, 17 Oct 2023 09:59:46 -0700 [thread overview]
Message-ID: <20231017165946.v4i2d4exyqwqq3bx@treble> (raw)
In-Reply-To: <20231017153222.GA707258@dev-arch.thelio-3990X>
Enabling CONFIG_KCSAN causes a panic during boot due to an "invalid
opcode" in __x86_return_thunk():
invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.6.0-rc2-00316-g91174087dcc7 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-14-g1e1da7a96300-prebuilt.qemu.org 04/01/2014
RIP: 0010:__x86_return_thunk+0x0/0x10
Code: e8 01 00 00 00 cc e8 01 00 00 00 cc 48 81 c4 80 00 00 00 65 48 c7 04 25 d0 ac 02 00 ff ff ff ff c3 cc 0f 1f 84 00 00 00 00 00 <0f> 0b cc cc cc cc cc cc cc cc cc cc cc cc cc cc e9 db 8c 8e fe 0f
RSP: 0018:ffffaef1c0013ed0 EFLAGS: 00010246
RAX: ffffffffa0e80eb0 RBX: ffffffffa0f05240 RCX: 0001ffffffffffff
RDX: 0000000000000551 RSI: ffffffffa0dcc64e RDI: ffffffffa0f05238
RBP: ffff8f93c11708e0 R08: ffffffffa1387280 R09: 0000000000000000
R10: 0000000000000282 R11: 0001ffffa0f05238 R12: 0000000000000002
R13: 0000000000000282 R14: 0000000000000001 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8f93df000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8f93d6c01000 CR3: 0000000015c2e000 CR4: 0000000000350ef0
The panic is triggered by the UD2 instruction which gets patched into
__x86_return_thunk() when alternatives are applied. After that point,
the default return thunk should no longer be used.
As David Kaplan describes, the issue 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.
Fixes: 91174087dcc7 ("x86/retpoline: Ensure default return thunk isn't used at runtime")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/lkml/20231016214810.GA3942238@dev-arch.thelio-3990X/
Debugged-by: David Kaplan <David.Kaplan@amd.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
init/Makefile | 1 +
scripts/Makefile.vmlinux | 1 +
2 files changed, 2 insertions(+)
diff --git a/init/Makefile b/init/Makefile
index ec557ada3c12..cbac576c57d6 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 3cd6ca15f390..c9f3e03124d7 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
--
2.41.0
next prev parent reply other threads:[~2023-10-17 16:59 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-10 17:10 [PATCH 0/3] Ensure default return thunk isn't used at runtime David Kaplan
2023-10-10 17:10 ` [PATCH 1/3] Revert "x86/retpoline: Remove .text..__x86.return_thunk section" David Kaplan
2023-10-10 17:48 ` Peter Zijlstra
2023-10-10 19:57 ` Josh Poimboeuf
2023-10-10 20:04 ` Borislav Petkov
2023-10-10 20:19 ` Josh Poimboeuf
2023-10-10 20:40 ` Kaplan, David
2023-10-10 21:22 ` Josh Poimboeuf
2023-10-11 7:41 ` Peter Zijlstra
2023-10-11 9:34 ` Borislav Petkov
2023-10-11 16:28 ` Josh Poimboeuf
2023-10-11 22:35 ` Peter Zijlstra
2023-10-11 22:42 ` Ingo Molnar
2023-10-12 2:27 ` Josh Poimboeuf
2023-10-12 2:47 ` [PATCH v2] objtool: Fix return thunk patching in retpolines Josh Poimboeuf
2023-10-12 6:25 ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-10-12 8:16 ` [PATCH v2] " Peter Zijlstra
2023-10-12 17:50 ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-10-20 11:37 ` tip-bot2 for Josh Poimboeuf
2023-10-12 8:16 ` [PATCH 1/3] Revert "x86/retpoline: Remove .text..__x86.return_thunk section" Peter Zijlstra
2023-10-10 17:10 ` [PATCH 2/3] x86/vdso: Run objtool on vdso32-setup David Kaplan
2023-10-12 17:50 ` [tip: x86/bugs] x86/vdso: Run objtool on vdso32-setup.o tip-bot2 for David Kaplan
2023-10-20 11:37 ` tip-bot2 for David Kaplan
2023-10-10 17:10 ` [PATCH 3/3] x86/retpoline: Ensure default return thunk isn't used at runtime David Kaplan
2023-10-10 19:36 ` Josh Poimboeuf
2023-10-10 20:14 ` Kaplan, David
2023-10-10 20:41 ` Josh Poimboeuf
2023-10-12 14:10 ` [PATCH -v2] " Borislav Petkov
2023-10-12 17:11 ` Josh Poimboeuf
2023-10-12 17:50 ` [tip: x86/bugs] " tip-bot2 for David Kaplan
2023-10-16 21:10 ` Nathan Chancellor
2023-10-16 21:29 ` Borislav Petkov
2023-10-16 21:48 ` Nathan Chancellor
2023-10-17 4:31 ` Kaplan, David
2023-10-17 5:28 ` Josh Poimboeuf
2023-10-17 13:54 ` Kaplan, David
2023-10-17 15:24 ` Nick Desaulniers
2023-10-17 15:26 ` Marco Elver
2023-10-17 15:32 ` Nathan Chancellor
2023-10-17 16:59 ` Josh Poimboeuf [this message]
2023-10-17 17:52 ` [tip: x86/bugs] x86/retpoline: Make sure there are no unconverted return thunks due to KCSAN tip-bot2 for Josh Poimboeuf
2023-10-20 11:37 ` tip-bot2 for Josh Poimboeuf
2023-10-18 13:23 ` [tip: x86/bugs] x86/retpoline: Ensure default return thunk isn't used at runtime Borislav Petkov
2023-10-18 13:38 ` Ingo Molnar
2023-10-18 15:12 ` Borislav Petkov
2023-10-18 15:54 ` Josh Poimboeuf
2023-10-18 17:55 ` Borislav Petkov
2023-10-18 18:14 ` Josh Poimboeuf
2023-10-18 18:22 ` Borislav Petkov
2023-10-18 18:39 ` Josh Poimboeuf
2023-10-18 18:44 ` Borislav Petkov
2023-10-18 19:14 ` Josh Poimboeuf
2023-10-18 20:04 ` Borislav Petkov
2023-10-18 20:37 ` Borislav Petkov
2023-10-19 6:35 ` Josh Poimboeuf
2023-10-19 6:59 ` Josh Poimboeuf
2023-10-19 14:15 ` Borislav Petkov
2023-10-19 14:21 ` Kaplan, David
2023-10-19 14:39 ` Borislav Petkov
2023-10-19 15:20 ` Josh Poimboeuf
2023-10-24 20:19 ` Borislav Petkov
2024-01-03 18:46 ` Borislav Petkov
2024-01-04 13:12 ` Borislav Petkov
2024-01-04 13:24 ` [PATCH -v2] " Borislav Petkov
2024-01-04 13:26 ` Borislav Petkov
2024-02-07 17:50 ` Josh Poimboeuf
2024-02-07 18:53 ` Borislav Petkov
2024-02-07 19:49 ` Josh Poimboeuf
2024-02-12 10:43 ` Borislav Petkov
2024-04-03 17:10 ` Klara Modin
2024-04-03 17:30 ` Borislav Petkov
2024-04-03 20:26 ` Klara Modin
2024-04-03 20:41 ` Borislav Petkov
2024-04-03 22:25 ` Klara Modin
2024-04-04 14:44 ` Borislav Petkov
2024-04-16 9:27 ` Borislav Petkov
2024-04-17 3:59 ` Klara Modin
2024-04-17 16:20 ` [tip: x86/urgent] x86/retpolines: Enable the default thunk warning only on relevant configs tip-bot2 for Borislav Petkov (AMD)
2023-10-19 7:43 ` [tip: x86/bugs] x86/retpoline: Ensure default return thunk isn't used at runtime Peter Zijlstra
2023-10-19 9:40 ` [tip: x86/bugs] Revert "x86/retpoline: Remove .text..__x86.return_thunk section" tip-bot2 for Borislav Petkov (AMD)
2023-10-19 9:40 ` [tip: x86/bugs] Revert "x86/retpoline: Ensure default return thunk isn't used at runtime" tip-bot2 for Borislav Petkov (AMD)
2024-02-12 14:13 ` [tip: x86/bugs] x86/retpoline: Ensure default return thunk isn't used at runtime tip-bot2 for Josh Poimboeuf
2024-02-15 3:20 ` Nathan Chancellor
2024-02-15 8:30 ` Nikolay Borisov
2024-02-15 15:53 ` Borislav Petkov
2024-02-16 5:42 ` Josh Poimboeuf
2024-02-16 21:27 ` Borislav Petkov
2024-02-20 5:57 ` [PATCH] x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o Josh Poimboeuf
2024-02-20 12:31 ` [tip: x86/core] " tip-bot2 for Josh Poimboeuf
2023-10-10 17:52 ` [PATCH 0/3] Ensure default return thunk isn't used at runtime Peter Zijlstra
2023-10-20 11:28 ` Subject: [PATCH] x86/retpoline: Document some thunk handling aspects (was: Re: [PATCH 0/3] Ensure default return thunk isn't used at runtime) Borislav Petkov
2023-10-20 11:37 ` [tip: x86/bugs] x86/retpoline: Document some thunk handling aspects tip-bot2 for Borislav Petkov (AMD)
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