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([2a0b:e7c0:0:107::70f]) by smtp.gmail.com with ESMTPSA id m6-20020aa7c486000000b0043a1255bc68sm7392391edq.94.2022.07.13.00.45.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 Jul 2022 00:45:27 -0700 (PDT) Message-ID: <63e23f80-033f-f64e-7522-2816debbc367@kernel.org> Date: Wed, 13 Jul 2022 09:45:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH 5.18 34/61] objtool: Update Retpoline validation Content-Language: en-US To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, "Peter Zijlstra (Intel)" , Borislav Petkov , Josh Poimboeuf , Thadeu Lima de Souza Cascardo References: <20220712183236.931648980@linuxfoundation.org> <20220712183238.342232911@linuxfoundation.org> From: Jiri Slaby In-Reply-To: <20220712183238.342232911@linuxfoundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 12. 07. 22, 20:39, Greg Kroah-Hartman wrote: > From: Peter Zijlstra > > commit 9bb2ec608a209018080ca262f771e6a9ff203b6f upstream. > > Update retpoline validation with the new CONFIG_RETPOLINE requirement of > not having bare naked RET instructions. Hi, this breaks compilation on i386: > arch/x86/kernel/../../x86/xen/xen-head.S:35: Error: no such instruction: `annotate_unret_safe' Config: https://raw.githubusercontent.com/openSUSE/kernel-source/stable/config/i386/pae And yeah, upstream¹⁾ is affected too. ¹⁾I am at commit b047602d579b4fb028128a525f056bbdc890e7f0. > Signed-off-by: Peter Zijlstra (Intel) > Signed-off-by: Borislav Petkov > Reviewed-by: Josh Poimboeuf > Signed-off-by: Borislav Petkov > Signed-off-by: Thadeu Lima de Souza Cascardo > Signed-off-by: Greg Kroah-Hartman > --- > arch/x86/include/asm/nospec-branch.h | 6 ++++++ > arch/x86/mm/mem_encrypt_boot.S | 2 ++ > arch/x86/xen/xen-head.S | 1 + > tools/objtool/check.c | 19 +++++++++++++------ > 4 files changed, 22 insertions(+), 6 deletions(-) > > --- a/arch/x86/include/asm/nospec-branch.h > +++ b/arch/x86/include/asm/nospec-branch.h > @@ -76,6 +76,12 @@ > .endm > > /* > + * (ab)use RETPOLINE_SAFE on RET to annotate away 'bare' RET instructions > + * vs RETBleed validation. > + */ > +#define ANNOTATE_UNRET_SAFE ANNOTATE_RETPOLINE_SAFE > + > +/* > * JMP_NOSPEC and CALL_NOSPEC macros can be used instead of a simple > * indirect jmp/call which may be susceptible to the Spectre variant 2 > * attack. > --- a/arch/x86/mm/mem_encrypt_boot.S > +++ b/arch/x86/mm/mem_encrypt_boot.S > @@ -66,6 +66,7 @@ SYM_FUNC_START(sme_encrypt_execute) > pop %rbp > > /* Offset to __x86_return_thunk would be wrong here */ > + ANNOTATE_UNRET_SAFE > ret > int3 > SYM_FUNC_END(sme_encrypt_execute) > @@ -154,6 +155,7 @@ SYM_FUNC_START(__enc_copy) > pop %r15 > > /* Offset to __x86_return_thunk would be wrong here */ > + ANNOTATE_UNRET_SAFE > ret > int3 > .L__enc_copy_end: > --- a/arch/x86/xen/xen-head.S > +++ b/arch/x86/xen/xen-head.S > @@ -26,6 +26,7 @@ SYM_CODE_START(hypercall_page) > .rept (PAGE_SIZE / 32) > UNWIND_HINT_FUNC > ANNOTATE_NOENDBR > + ANNOTATE_UNRET_SAFE > ret > /* > * Xen will write the hypercall page, and sort out ENDBR. > --- a/tools/objtool/check.c > +++ b/tools/objtool/check.c > @@ -2114,8 +2114,9 @@ static int read_retpoline_hints(struct o > } > > if (insn->type != INSN_JUMP_DYNAMIC && > - insn->type != INSN_CALL_DYNAMIC) { > - WARN_FUNC("retpoline_safe hint not an indirect jump/call", > + insn->type != INSN_CALL_DYNAMIC && > + insn->type != INSN_RETURN) { > + WARN_FUNC("retpoline_safe hint not an indirect jump/call/ret", > insn->sec, insn->offset); > return -1; > } > @@ -3648,7 +3649,8 @@ static int validate_retpoline(struct obj > > for_each_insn(file, insn) { > if (insn->type != INSN_JUMP_DYNAMIC && > - insn->type != INSN_CALL_DYNAMIC) > + insn->type != INSN_CALL_DYNAMIC && > + insn->type != INSN_RETURN) > continue; > > if (insn->retpoline_safe) > @@ -3663,9 +3665,14 @@ static int validate_retpoline(struct obj > if (!strcmp(insn->sec->name, ".init.text") && !module) > continue; > > - WARN_FUNC("indirect %s found in RETPOLINE build", > - insn->sec, insn->offset, > - insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); > + if (insn->type == INSN_RETURN) { > + WARN_FUNC("'naked' return found in RETPOLINE build", > + insn->sec, insn->offset); > + } else { > + WARN_FUNC("indirect %s found in RETPOLINE build", > + insn->sec, insn->offset, > + insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); > + } > > warnings++; > } > > -- js suse labs