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 546282DF73; Mon, 8 Apr 2024 13:20:42 +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=1712582442; cv=none; b=EyWs6lTKwucMNu1yqsVGs3JB2oc2IW0Cx5SjS2yHqMLFgNfjmSIVeHQCQbjTDxDTkqrvSOLQuTwqt+Y6BXt0rHM5r0dzxYPlVikxhXEF8j9t71Un/M9Y2ol2pJt9VoE22suXCyiz4Lt2kXw3xV/waiTxd8lzy9IgvRYxuRCSoaA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712582442; c=relaxed/simple; bh=8c7UNISZV5nZFwVc/2X0j0FJL4wqFtfm0dOQ0ut3I78=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=l8zSCLVMpBrp0USwpoloyFdalmScy4rOt02VSgqlmnNg9FeEnKC1kSTOG33CtFjn2NNyYaD43OdKH9YbhuKqAl73lPZ0LJkRFmph0UN0i+XIjOgqtW2G6k73a3nUsJpndMIXmWXRvQ1NwqOiaKwKSk2a/wXPnC5ArVz0EGF8nwM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xG2N6jUf; 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="xG2N6jUf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CEE4DC433F1; Mon, 8 Apr 2024 13:20:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1712582442; bh=8c7UNISZV5nZFwVc/2X0j0FJL4wqFtfm0dOQ0ut3I78=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xG2N6jUfkh9+LoFDvKFVsVd0lKurYzJhv52zS/+QB/1/kgGWKYa00D7iiYYJWuPPM MBdM712VAi4TMLJQKYWj4ybHqSfq4NFOnDrGrYid7SBCIULWTknqfMSkj0rD7c7/Xs Dg4rRJQxfzglx7cHQ8ecYmI3FGqIns5l0MoSo4oo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Borislav Petkov (AMD)" , Ingo Molnar , stable@kernel.org, Linus Torvalds Subject: [PATCH 6.6 093/252] x86/bugs: Fix the SRSO mitigation on Zen3/4 Date: Mon, 8 Apr 2024 14:56:32 +0200 Message-ID: <20240408125309.542260264@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240408125306.643546457@linuxfoundation.org> References: <20240408125306.643546457@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Borislav Petkov (AMD)" Commit 4535e1a4174c4111d92c5a9a21e542d232e0fcaa upstream. 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 Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/asm-prototypes.h | 1 + arch/x86/include/asm/nospec-branch.h | 21 ++++++++++++++++----- arch/x86/lib/retpoline.S | 10 +++++----- 3 files changed, 22 insertions(+), 10 deletions(-) --- a/arch/x86/include/asm/asm-prototypes.h +++ b/arch/x86/include/asm/asm-prototypes.h @@ -13,6 +13,7 @@ #include #include #include +#include #ifndef CONFIG_X86_CMPXCHG64 extern void cmpxchg8b_emu(void); --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -271,11 +271,20 @@ .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_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_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 @@ -291,8 +300,8 @@ .macro __UNTRAIN_RET ibpb_feature, call_depth_insns #if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_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 @@ -351,6 +360,8 @@ extern void retbleed_return_thunk(void); static inline void retbleed_return_thunk(void) {} #endif +extern void srso_alias_untrain_ret(void); + #ifdef CONFIG_CPU_SRSO extern void srso_return_thunk(void); extern void srso_alias_return_thunk(void); --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -218,10 +218,12 @@ 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_CPU_SRSO */ #define JMP_SRSO_UNTRAIN_RET "ud2" -#define JMP_SRSO_ALIAS_UNTRAIN_RET "ud2" +/* Dummy for the alternative in CALL_UNTRAIN_RET. */ +SYM_CODE_START(srso_alias_untrain_ret) + RET +SYM_FUNC_END(srso_alias_untrain_ret) #endif /* CONFIG_CPU_SRSO */ #ifdef CONFIG_CPU_UNRET_ENTRY @@ -314,9 +316,7 @@ __EXPORT_THUNK(retbleed_untrain_ret) #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_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)