From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1EFC864F for ; Sat, 30 Mar 2024 09:46:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711791991; cv=none; b=BzZMrs9UR/TaACTW73z7aK5Kv+r9r5HbU3Ty9RKdevqxYJn8sRs8WOWTniji4T6MJ+K1XbZwP8+PRiBKaFtN9JKoQac6Z6WVpug83U6caB/vtkRx1xM3K348+iOGvDe2hA2mLRwS3wdd/T/vT3eSevI2ohMvyNK/LD4gYoAKx1s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711791991; c=relaxed/simple; bh=XBNM6zSbJljgEldMq7n9uDsTgYx/MLhcLJavokCoxj8=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=gZ5RRMe27d7Yo0y49H5R8LIzVb8NXhRCp0zsSOWwE6Mr3NdrcGLmyTRp7Dqw6WgZl6dsFYqJ6oockZLmfQ/LwjUmpEAusiTQhjhWDIeXBSwrV1y+ao+5+cq00fdcJ/sx/qYx9OsD9k8qepm69xOx6AosZwUxd6TLbrdkDnGLztM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Z7NXUklG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Z7NXUklG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E6B10C433C7; Sat, 30 Mar 2024 09:46:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1711791990; bh=XBNM6zSbJljgEldMq7n9uDsTgYx/MLhcLJavokCoxj8=; h=Subject:To:Cc:From:Date:From; b=Z7NXUklGdrGNBu2lQkpHrw08wMsgNQ9pvd9t+5V1yEwH44CkzbG/zd1pBwIvzSTP9 ddHAC2frTwxV3fomlk2V8mLM/WDvg9hfi9PD+tmNDs8YFF3Y9hLF/vxenUc6qX2Fei P4rk6XGSHr1Wq3YjUJd9lrM6A22vEFiAV19mp4NQ= Subject: FAILED: patch "[PATCH] x86/bugs: Fix the SRSO mitigation on Zen3/4" failed to apply to 6.8-stable tree To: bp@alien8.de,mingo@kernel.org,torvalds@linux-foundation.org Cc: From: Date: Sat, 30 Mar 2024 10:46:27 +0100 Message-ID: <2024033027-tapered-curly-3516@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.8-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.8.y git checkout FETCH_HEAD git cherry-pick -x 4535e1a4174c4111d92c5a9a21e542d232e0fcaa # git commit -s git send-email --to '' --in-reply-to '2024033027-tapered-curly-3516@gregkh' --subject-prefix 'PATCH 6.8.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 4535e1a4174c4111d92c5a9a21e542d232e0fcaa Mon Sep 17 00:00:00 2001 From: "Borislav Petkov (AMD)" Date: Thu, 28 Mar 2024 13:59:05 +0100 Subject: [PATCH] x86/bugs: Fix the SRSO mitigation on Zen3/4 The original version of the mitigation would patch in the calls to the untraining routines directly. That is, the alternative() in UNTRAIN_RET will patch in the CALL to srso_alias_untrain_ret() directly. However, even if commit e7c25c441e9e ("x86/cpu: Cleanup the untrain mess") meant well in trying to clean up the situation, due to micro- architectural reasons, the untraining routine srso_alias_untrain_ret() must be the target of a CALL instruction and not of a JMP instruction as it is done now. Reshuffle the alternative macros to accomplish that. Fixes: e7c25c441e9e ("x86/cpu: Cleanup the untrain mess") Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Ingo Molnar Cc: stable@kernel.org Signed-off-by: Linus Torvalds diff --git a/arch/x86/include/asm/asm-prototypes.h b/arch/x86/include/asm/asm-prototypes.h index 076bf8dee702..25466c4d2134 100644 --- a/arch/x86/include/asm/asm-prototypes.h +++ b/arch/x86/include/asm/asm-prototypes.h @@ -14,6 +14,7 @@ #include #include #include +#include #ifndef CONFIG_X86_CMPXCHG64 extern void cmpxchg8b_emu(void); diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index fc3a8a3c7ffe..170c89ed22fc 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -262,11 +262,20 @@ .Lskip_rsb_\@: .endm +/* + * The CALL to srso_alias_untrain_ret() must be patched in directly at + * the spot where untraining must be done, ie., srso_alias_untrain_ret() + * must be the target of a CALL instruction instead of indirectly + * jumping to a wrapper which then calls it. Therefore, this macro is + * called outside of __UNTRAIN_RET below, for the time being, before the + * kernel can support nested alternatives with arbitrary nesting. + */ +.macro CALL_UNTRAIN_RET #if defined(CONFIG_MITIGATION_UNRET_ENTRY) || defined(CONFIG_MITIGATION_SRSO) -#define CALL_UNTRAIN_RET "call entry_untrain_ret" -#else -#define CALL_UNTRAIN_RET "" + ALTERNATIVE_2 "", "call entry_untrain_ret", X86_FEATURE_UNRET, \ + "call srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS #endif +.endm /* * Mitigate RETBleed for AMD/Hygon Zen uarch. Requires KERNEL CR3 because the @@ -282,8 +291,8 @@ .macro __UNTRAIN_RET ibpb_feature, call_depth_insns #if defined(CONFIG_MITIGATION_RETHUNK) || defined(CONFIG_MITIGATION_IBPB_ENTRY) VALIDATE_UNRET_END - ALTERNATIVE_3 "", \ - CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ + CALL_UNTRAIN_RET + ALTERNATIVE_2 "", \ "call entry_ibpb", \ibpb_feature, \ __stringify(\call_depth_insns), X86_FEATURE_CALL_DEPTH #endif @@ -342,6 +351,8 @@ extern void retbleed_return_thunk(void); static inline void retbleed_return_thunk(void) {} #endif +extern void srso_alias_untrain_ret(void); + #ifdef CONFIG_MITIGATION_SRSO extern void srso_return_thunk(void); extern void srso_alias_return_thunk(void); diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index 721b528da9ac..02cde194a99e 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -163,6 +163,7 @@ SYM_CODE_START_NOALIGN(srso_alias_untrain_ret) lfence jmp srso_alias_return_thunk SYM_FUNC_END(srso_alias_untrain_ret) +__EXPORT_THUNK(srso_alias_untrain_ret) .popsection .pushsection .text..__x86.rethunk_safe @@ -224,10 +225,12 @@ SYM_CODE_START(srso_return_thunk) SYM_CODE_END(srso_return_thunk) #define JMP_SRSO_UNTRAIN_RET "jmp srso_untrain_ret" -#define JMP_SRSO_ALIAS_UNTRAIN_RET "jmp srso_alias_untrain_ret" #else /* !CONFIG_MITIGATION_SRSO */ +/* Dummy for the alternative in CALL_UNTRAIN_RET. */ +SYM_CODE_START(srso_alias_untrain_ret) + RET +SYM_FUNC_END(srso_alias_untrain_ret) #define JMP_SRSO_UNTRAIN_RET "ud2" -#define JMP_SRSO_ALIAS_UNTRAIN_RET "ud2" #endif /* CONFIG_MITIGATION_SRSO */ #ifdef CONFIG_MITIGATION_UNRET_ENTRY @@ -319,9 +322,7 @@ SYM_FUNC_END(retbleed_untrain_ret) #if defined(CONFIG_MITIGATION_UNRET_ENTRY) || defined(CONFIG_MITIGATION_SRSO) SYM_FUNC_START(entry_untrain_ret) - ALTERNATIVE_2 JMP_RETBLEED_UNTRAIN_RET, \ - JMP_SRSO_UNTRAIN_RET, X86_FEATURE_SRSO, \ - JMP_SRSO_ALIAS_UNTRAIN_RET, X86_FEATURE_SRSO_ALIAS + ALTERNATIVE JMP_RETBLEED_UNTRAIN_RET, JMP_SRSO_UNTRAIN_RET, X86_FEATURE_SRSO SYM_FUNC_END(entry_untrain_ret) __EXPORT_THUNK(entry_untrain_ret)