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 A676E21ABA5 for ; Thu, 19 Jun 2025 09:04:34 +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=1750323879; cv=none; b=uiIInc5+XWhglsv5XKMFNM0iLGlNho3yYISmiz45HuS3C2ngqwK4myQN2eKo6KAvy29aiXeCblVJErou+kcXLj7SuqdgtygVXqicFvbMm0xG1nhXs/+gbBGvcGeZTkddv07WPBw8pUqJn3uK24WkdJhyxr4A7oYzqYkAyz1sRN4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750323879; c=relaxed/simple; bh=6fM43ZIp8MSP8IEBhmAedyDNUT3qyinzVJyrFv2x3UE=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=VH1152sXD9B38rBnLi75qQYV3aYDX0V2inAStOhjQlfB2XeNBB/WKtYfLWpJ5ivDF+WsQgbq01ZHdZ5pograMw+FL8pID3NrdHtcgOkJuKQupT0f+m+6tgDHI502mKoCU6fEdkHAqveTBsV3tS8TqRGR1PIZG/2J14u3XTf5Jow= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=u55IbEnx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="u55IbEnx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ACCF0C4CEEA; Thu, 19 Jun 2025 09:04:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750323874; bh=6fM43ZIp8MSP8IEBhmAedyDNUT3qyinzVJyrFv2x3UE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=u55IbEnxuuvzt4fupx87hUPC9frVHaVi2ruqSwTvpAORhvCpyA8aJwB3nAtNabZNh /Hoxhzl57E/+P0GPUrGsWHRv23SyMS8RGGHan3a8hppIlU22odzF4XLJTnidSb6Jb7 tT2VZMhDmo3cGFsx99d7dJuKVFQ8LfCZ/p0W8fAO1gPJTPUeblgZfDkIsFYS8ni92A RRDGJNbfVGRWURE/Y7Db2y4CyeTn/a6fg9jskORJlBf9+aZJvzNpybp6NYXvp0TBeq Ln7UuPx3Ihb78Szaf6OTP8hoDs/ls3DTQOtNzDCvqDP+U4nSIlrUNnyVC49jeVKZ+1 eStTpLiu6PDjg== From: Sasha Levin To: stable@vger.kernel.org Cc: Pawan Gupta , Sasha Levin Subject: Re: [PATCH 5.10 v2 11/16] x86/its: Enable Indirect Target Selection mitigation Date: Thu, 19 Jun 2025 05:04:32 -0400 Message-Id: <20250618182547-be61423b7dacd3b5@stable.kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250617-its-5-10-v2-11-3e925a1512a1@linux.intel.com> References: Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit [ Sasha's backport helper bot ] Hi, ✅ All tests passed successfully. No issues detected. No action required from the submitter. The upstream commit SHA1 provided is correct: f4818881c47fd91fcb6d62373c57c7844e3de1c0 Status in newer kernel trees: 6.15.y | Present (exact SHA1) 6.12.y | Present (different SHA1: 68d59e9ba384) 6.6.y | Present (different SHA1: f7ef7f6ccf2b) 6.1.y | Present (different SHA1: b1701fee52d1) 5.15.y | Present (different SHA1: e30bcefa93a6) Note: The patch differs from the upstream commit: --- 1: f4818881c47fd ! 1: d14c05df3083a x86/its: Enable Indirect Target Selection mitigation @@ Metadata ## Commit message ## x86/its: Enable Indirect Target Selection mitigation + commit f4818881c47fd91fcb6d62373c57c7844e3de1c0 upstream. + Indirect Target Selection (ITS) is a bug in some pre-ADL Intel CPUs with eIBRS. It affects prediction of indirect branch and RETs in the lower half of cacheline. Due to ITS such branches may get wrongly predicted @@ Commit message spectre-v2 lfence;jmp mitigation. Moreover, it is less practical to deploy lfence;jmp mitigation on ITS affected parts anyways. - Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Josh Poimboeuf Reviewed-by: Alexandre Chartre + Signed-off-by: Pawan Gupta ## Documentation/ABI/testing/sysfs-devices-system-cpu ## @@ Documentation/ABI/testing/sysfs-devices-system-cpu: Description: information about CPUs heterogeneity. @@ Documentation/admin-guide/kernel-parameters.txt Format: Run specified binary instead of /sbin/init as init @@ + improves system performance, but it may also expose users to several CPU vulnerabilities. - Equivalent to: if nokaslr then kpti=0 [ARM64] - gather_data_sampling=off [X86] + Equivalent to: gather_data_sampling=off [X86] + indirect_target_selection=off [X86] + kpti=0 [ARM64] kvm.nx_huge_pages=off [X86] l1tf=off [X86] - mds=off [X86] ## arch/x86/kernel/cpu/bugs.c ## -@@ arch/x86/kernel/cpu/bugs.c: static void __init srbds_select_mitigation(void); - static void __init l1d_flush_select_mitigation(void); - static void __init srso_select_mitigation(void); +@@ arch/x86/kernel/cpu/bugs.c: static void __init mmio_select_mitigation(void); + static void __init srbds_select_mitigation(void); static void __init gds_select_mitigation(void); + static void __init srso_select_mitigation(void); +static void __init its_select_mitigation(void); /* The base value of the SPEC_CTRL MSR without task-specific bits set */ u64 x86_spec_ctrl_base; @@ arch/x86/kernel/cpu/bugs.c: static DEFINE_MUTEX(spec_ctrl_mutex); - void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk; + void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk; +static void __init set_return_thunk(void *thunk) +{ @@ arch/x86/kernel/cpu/bugs.c: void __init cpu_select_mitigations(void) /* @@ arch/x86/kernel/cpu/bugs.c: static void __init retbleed_select_mitigation(void) - setup_force_cpu_cap(X86_FEATURE_RETHUNK); setup_force_cpu_cap(X86_FEATURE_UNRET); -- x86_return_thunk = retbleed_return_thunk; -+ set_return_thunk(retbleed_return_thunk); + if (IS_ENABLED(CONFIG_RETHUNK)) +- x86_return_thunk = retbleed_return_thunk; ++ set_return_thunk(retbleed_return_thunk); if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) -@@ arch/x86/kernel/cpu/bugs.c: static void __init retbleed_select_mitigation(void) - setup_force_cpu_cap(X86_FEATURE_RETHUNK); - setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH); - -- x86_return_thunk = call_depth_return_thunk; -+ set_return_thunk(call_depth_return_thunk); - break; - - default: @@ arch/x86/kernel/cpu/bugs.c: static void __init retbleed_select_mitigation(void) pr_info("%s\n", retbleed_strings[retbleed_mitigation]); } @@ arch/x86/kernel/cpu/bugs.c: static void __init retbleed_select_mitigation(void) +enum its_mitigation { + ITS_MITIGATION_OFF, + ITS_MITIGATION_ALIGNED_THUNKS, -+ ITS_MITIGATION_RETPOLINE_STUFF, +}; + +static const char * const its_strings[] = { + [ITS_MITIGATION_OFF] = "Vulnerable", + [ITS_MITIGATION_ALIGNED_THUNKS] = "Mitigation: Aligned branch/return thunks", -+ [ITS_MITIGATION_RETPOLINE_STUFF] = "Mitigation: Retpolines, Stuffing RSB", +}; + +static enum its_mitigation its_mitigation __ro_after_init = ITS_MITIGATION_ALIGNED_THUNKS; @@ arch/x86/kernel/cpu/bugs.c: static void __init retbleed_select_mitigation(void) + return; + } + -+ /* Retpoline+CDT mitigates ITS, bail out */ -+ if (boot_cpu_has(X86_FEATURE_RETPOLINE) && -+ boot_cpu_has(X86_FEATURE_CALL_DEPTH)) { -+ its_mitigation = ITS_MITIGATION_RETPOLINE_STUFF; -+ goto out; -+ } -+ + /* Exit early to avoid irrelevant warnings */ + if (cmd == ITS_CMD_OFF) { + its_mitigation = ITS_MITIGATION_OFF; @@ arch/x86/kernel/cpu/bugs.c: static void __init retbleed_select_mitigation(void) + its_mitigation = ITS_MITIGATION_OFF; + goto out; + } -+ if (!IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) || -+ !IS_ENABLED(CONFIG_MITIGATION_RETHUNK)) { ++ if (!IS_ENABLED(CONFIG_RETPOLINE) || !IS_ENABLED(CONFIG_RETHUNK)) { + pr_err("WARNING: ITS mitigation depends on retpoline and rethunk support\n"); + its_mitigation = ITS_MITIGATION_OFF; + goto out; @@ arch/x86/kernel/cpu/bugs.c: static void __init srso_select_mitigation(void) - x86_return_thunk = srso_return_thunk; + set_return_thunk(srso_return_thunk); } - if (has_microcode) - srso_mitigation = SRSO_MITIGATION_SAFE_RET; + srso_mitigation = SRSO_MITIGATION_SAFE_RET; + } else { @@ arch/x86/kernel/cpu/bugs.c: static ssize_t rfds_show_state(char *buf) return sysfs_emit(buf, "%s\n", rfds_strings[rfds_mitigation]); } @@ arch/x86/kernel/cpu/bugs.c: ssize_t cpu_show_reg_file_data_sampling(struct devic + return cpu_show_common(dev, attr, buf, X86_BUG_ITS); +} #endif - - void __warn_thunk(void) ## drivers/base/cpu.c ## -@@ drivers/base/cpu.c: CPU_SHOW_VULN_FALLBACK(spec_rstack_overflow); - CPU_SHOW_VULN_FALLBACK(gds); - CPU_SHOW_VULN_FALLBACK(reg_file_data_sampling); - CPU_SHOW_VULN_FALLBACK(ghostwrite); -+CPU_SHOW_VULN_FALLBACK(indirect_target_selection); +@@ drivers/base/cpu.c: ssize_t __weak cpu_show_reg_file_data_sampling(struct device *dev, + return sysfs_emit(buf, "Not affected\n"); + } ++ssize_t __weak cpu_show_indirect_target_selection(struct device *dev, ++ struct device_attribute *attr, char *buf) ++{ ++ return sysfs_emit(buf, "Not affected\n"); ++} ++ static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL); static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL); -@@ drivers/base/cpu.c: static DEVICE_ATTR(spec_rstack_overflow, 0444, cpu_show_spec_rstack_overflow, NU + static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL); +@@ drivers/base/cpu.c: static DEVICE_ATTR(retbleed, 0444, cpu_show_retbleed, NULL); static DEVICE_ATTR(gather_data_sampling, 0444, cpu_show_gds, NULL); + static DEVICE_ATTR(spec_rstack_overflow, 0444, cpu_show_spec_rstack_overflow, NULL); static DEVICE_ATTR(reg_file_data_sampling, 0444, cpu_show_reg_file_data_sampling, NULL); - static DEVICE_ATTR(ghostwrite, 0444, cpu_show_ghostwrite, NULL); +static DEVICE_ATTR(indirect_target_selection, 0444, cpu_show_indirect_target_selection, NULL); static struct attribute *cpu_root_vulnerabilities_attrs[] = { &dev_attr_meltdown.attr, @@ drivers/base/cpu.c: static struct attribute *cpu_root_vulnerabilities_attrs[] = { &dev_attr_gather_data_sampling.attr, + &dev_attr_spec_rstack_overflow.attr, &dev_attr_reg_file_data_sampling.attr, - &dev_attr_ghostwrite.attr, + &dev_attr_indirect_target_selection.attr, NULL }; @@ drivers/base/cpu.c: static struct attribute *cpu_root_vulnerabilities_attrs[] = ## include/linux/cpu.h ## @@ include/linux/cpu.h: extern ssize_t cpu_show_gds(struct device *dev, + struct device_attribute *attr, char *buf); extern ssize_t cpu_show_reg_file_data_sampling(struct device *dev, struct device_attribute *attr, char *buf); - extern ssize_t cpu_show_ghostwrite(struct device *dev, struct device_attribute *attr, char *buf); +extern ssize_t cpu_show_indirect_target_selection(struct device *dev, + struct device_attribute *attr, char *buf); --- Results of testing on various branches: | Branch | Patch Apply | Build Test | |---------------------------|-------------|------------| | stable/linux-5.15.y | Success | Success |