diff options
| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2024-02-19 21:57:18 -0800 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2024-02-20 13:26:10 +0100 |
| commit | b388e57d4628eb22782bdad4cd5b83ca87a1b7c9 (patch) | |
| tree | 78b939f11fb63fc7afbe5174be160df8c515d95f /arch/x86/entry | |
| parent | 4589f199eb68afd462bd792f730c7936fe3dafb5 (diff) | |
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@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240215032049.GA3944823@dev-arch.thelio-3990X
Diffstat (limited to 'arch/x86/entry')
| -rw-r--r-- | arch/x86/entry/vdso/Makefile | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile index c4df99aa1615..b80f4bbe4f75 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) |