[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <170843230884.398.17338035419021257054.tip-bot2@tip-bot2>
Date: Tue, 20 Feb 2024 12:31:48 -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>,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject:
[tip: x86/core] x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o
The following commit has been merged into the x86/core branch of tip:
Commit-ID: b388e57d4628eb22782bdad4cd5b83ca87a1b7c9
Gitweb: https://git.kernel.org/tip/b388e57d4628eb22782bdad4cd5b83ca87a1b7c9
Author: Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate: Mon, 19 Feb 2024 21:57:18 -08:00
Committer: Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Tue, 20 Feb 2024 13:26:10 +01:00
x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o
For CONFIG_RETHUNK kernels, objtool annotates all the function return
sites so they can be patched during boot. By design, after
apply_returns() is called, all tail-calls to the compiler-generated
default return thunk (__x86_return_thunk) should be patched out and
replaced with whatever's needed for any mitigations (or lack thereof).
The commit
4461438a8405 ("x86/retpoline: Ensure default return thunk isn't used at runtime")
adds a runtime check and a WARN_ONCE() if the default return thunk ever
gets executed after alternatives have been applied. This warning is
a sanity check to make sure objtool and apply_returns() are doing their
job.
As Nathan reported, that check found something:
Unpatched return thunk in use. This should not happen!
WARNING: CPU: 0 PID: 1 at arch/x86/kernel/cpu/bugs.c:2856 __warn_thunk+0x27/0x40
RIP: 0010:__warn_thunk+0x27/0x40
Call Trace:
<TASK>
? show_regs
? __warn
? __warn_thunk
? report_bug
? console_unlock
? handle_bug
? exc_invalid_op
? asm_exc_invalid_op
? ia32_binfmt_init
? __warn_thunk
warn_thunk_thunk
do_one_initcall
kernel_init_freeable
? __pfx_kernel_init
kernel_init
ret_from_fork
? __pfx_kernel_init
ret_from_fork_asm
</TASK>
Boris debugged to find that the unpatched return site was in
init_vdso_image_64(), and its translation unit wasn't being analyzed by
objtool, so it never got annotated. So it got ignored by
apply_returns().
This is only a minor issue, as this function is only called during boot.
Still, objtool needs full visibility to the kernel. Fix it by enabling
objtool on vdso-image-{32,64}.o.
Note this problem can only be seen with !CONFIG_X86_KERNEL_IBT, as that
requires objtool to run individually on all translation units rather on
vmlinux.o.
[ bp: Massage commit message. ]
Reported-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Link: https://lore.kernel.org/r/20240215032049.GA3944823@dev-arch.thelio-3990X
---
arch/x86/entry/vdso/Makefile | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index c4df99a..b80f4bb 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -34,8 +34,12 @@ obj-y += vma.o extable.o
KASAN_SANITIZE_vma.o := y
UBSAN_SANITIZE_vma.o := y
KCSAN_SANITIZE_vma.o := y
-OBJECT_FILES_NON_STANDARD_vma.o := n
-OBJECT_FILES_NON_STANDARD_extable.o := n
+
+OBJECT_FILES_NON_STANDARD_extable.o := n
+OBJECT_FILES_NON_STANDARD_vdso-image-32.o := n
+OBJECT_FILES_NON_STANDARD_vdso-image-64.o := n
+OBJECT_FILES_NON_STANDARD_vdso32-setup.o := n
+OBJECT_FILES_NON_STANDARD_vma.o := n
# vDSO images to build
vdso_img-$(VDSO64-y) += 64
@@ -43,7 +47,6 @@ vdso_img-$(VDSOX32-y) += x32
vdso_img-$(VDSO32-y) += 32
obj-$(VDSO32-y) += vdso32-setup.o
-OBJECT_FILES_NON_STANDARD_vdso32-setup.o := n
vobjs := $(foreach F,$(vobjs-y),$(obj)/$F)
vobjs32 := $(foreach F,$(vobjs32-y),$(obj)/$F)
Powered by blists - more mailing lists