[PATCH RESEND 0/6] arm64: add support for generic cpu vulnerabilities

[PATCH RESEND 0/6] arm64: add support for generic cpu vulnerabilities

[Mian Yousaf Kaukab]

GENERIC_CPU_VULNERABILITIES provide a common way to figure out if a
system is affected by vulnerabilities like meltdown and other variants
of spectre. This small series adds support for it in arm64.

Thank you,

Best regards,
Yousaf

Mian Yousaf Kaukab (6):
  arm64: kpti: move check for non-vulnerable CPUs to a function
  arm64: add sysfs vulnerability show for meltdown
  arm64: add sysfs vulnerability show for spectre v1
  arm64: add sysfs vulnerability show for spectre v2
  arm64: add sysfs vulnerability show for speculative store bypass
  arm64: enable generic CPU vulnerabilites support

 arch/arm64/Kconfig                  |  1 +
 arch/arm64/include/asm/cpufeature.h | 16 +++++++
 arch/arm64/kernel/cpu_errata.c      | 84 ++++++++++++++++++++++++++++++++++++-
 arch/arm64/kernel/cpufeature.c      |  9 +---
 4 files changed, 101 insertions(+), 9 deletions(-)

-- 
2.11.0

[PATCH RESEND 1/6] arm64: kpti: move check for non-vulnerable CPUs to a function

[Mian Yousaf Kaukab]

Prepare to call it in generic cpu vulnerabilities support.

Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 arch/arm64/include/asm/cpufeature.h | 16 ++++++++++++++++
 arch/arm64/kernel/cpufeature.c      |  9 +--------
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 1717ba1db35d..0b0b5b3e36ba 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -530,6 +530,22 @@ void arm64_set_ssbd_mitigation(bool state);
 static inline void arm64_set_ssbd_mitigation(bool state) {}
 #endif
 
+static inline bool is_cpu_meltdown_safe(void)
+{
+	/* List of CPUs that are not vulnerable and don't need KPTI */
+	static const struct midr_range kpti_safe_list[] = {
+		MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
+		MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
+		{ /* sentinel */ }
+	};
+
+	/* Don't force KPTI for CPUs that are not vulnerable */
+	if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))
+		return true;
+
+	return false;
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index e238b7932096..6a94f8bce35a 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -865,12 +865,6 @@ static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */
 static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 				int scope)
 {
-	/* List of CPUs that are not vulnerable and don't need KPTI */
-	static const struct midr_range kpti_safe_list[] = {
-		MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
-		MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
-		{ /* sentinel */ }
-	};
 	char const *str = "command line option";
 
 	/*
@@ -894,8 +888,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE))
 		return true;
 
-	/* Don't force KPTI for CPUs that are not vulnerable */
-	if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))
+	if (is_cpu_meltdown_safe())
 		return false;
 
 	/* Defer to CPU feature registers */
-- 
2.11.0

[PATCH RESEND 2/6] arm64: add sysfs vulnerability show for meltdown

[Mian Yousaf Kaukab]

Checking CSV3 support directly in case CONFIG_UNMAP_KERNEL_AT_EL0
is not enabled.

Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 arch/arm64/kernel/cpu_errata.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index dec10898d688..996edb4e18ad 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -22,6 +22,7 @@
 #include <asm/cpu.h>
 #include <asm/cputype.h>
 #include <asm/cpufeature.h>
+#include <asm/mmu.h>
 
 static bool __maybe_unused
 is_affected_midr_range(const struct arm64_cpu_capabilities *entry, int scope)
@@ -683,3 +684,26 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 	{
 	}
 };
+
+#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
+
+ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	u64 pfr0;
+	u32 csv3;
+
+	if (arm64_kernel_unmapped_at_el0())
+		return sprintf(buf, "Mitigation: KPTI\n");
+
+	pfr0 = read_cpuid(ID_AA64PFR0_EL1);
+	csv3 = cpuid_feature_extract_unsigned_field(pfr0,
+			ID_AA64PFR0_CSV3_SHIFT);
+
+	if (csv3 || is_cpu_meltdown_safe())
+		return sprintf(buf, "Not affected\n");
+
+	return sprintf(buf, "Vulnerable\n");
+}
+
+#endif
-- 
2.11.0

[PATCH RESEND 3/6] arm64: add sysfs vulnerability show for spectre v1

[Mian Yousaf Kaukab]

Hard-coded since patches are merged and there are no configuration
options.

Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 arch/arm64/kernel/cpu_errata.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 996edb4e18ad..92616431ae4e 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -706,4 +706,10 @@ ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr,
 	return sprintf(buf, "Vulnerable\n");
 }
 
+ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	return sprintf(buf, "Mitigation: __user pointer sanitization\n");
+}
+
 #endif
-- 
2.11.0

[PATCH RESEND 4/6] arm64: add sysfs vulnerability show for spectre v2

[Mian Yousaf Kaukab]

Only report mitigation present if hardening callback has been
successfully installed.

Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 arch/arm64/kernel/cpu_errata.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 92616431ae4e..8469d3be7b15 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -481,7 +481,8 @@ multi_entry_cap_cpu_enable(const struct arm64_cpu_capabilities *entry)
 			caps->cpu_enable(caps);
 }
 
-#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
+#if defined(CONFIG_HARDEN_BRANCH_PREDICTOR) || \
+	defined(CONFIG_GENERIC_CPU_VULNERABILITIES)
 
 /*
  * List of CPUs where we need to issue a psci call to
@@ -712,4 +713,35 @@ ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr,
 	return sprintf(buf, "Mitigation: __user pointer sanitization\n");
 }
 
+ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	u64 pfr0;
+	struct bp_hardening_data *data;
+
+	pfr0 = read_cpuid(ID_AA64PFR0_EL1);
+	if (cpuid_feature_extract_unsigned_field(pfr0, ID_AA64PFR0_CSV2_SHIFT))
+		return sprintf(buf, "Not affected\n");
+
+	if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR)) {
+		/*
+		 * Hardware is vulnerable. Lets check if bp hardening callback
+		 * has been successfully installed
+		 */
+		data = arm64_get_bp_hardening_data();
+		if (data && data->fn)
+			return sprintf(buf,
+				"Mitigation: Branch predictor hardening");
+		else
+			/* For example SMCCC_VERSION_1_0 */
+			return sprintf(buf, "Vulnerable\n");
+	}
+
+	/* In case CONFIG_HARDEN_BRANCH_PREDICTOR is not enabled */
+	if (is_midr_in_range_list(read_cpuid_id(), arm64_bp_harden_smccc_cpus))
+		return sprintf(buf, "Vulnerable\n");
+
+	return sprintf(buf, "Not affected\n");
+}
+
 #endif
-- 
2.11.0

[PATCH RESEND 5/6] arm64: add sysfs vulnerability show for speculative store bypass

[Mian Yousaf Kaukab]

Return status based no ssbd_state. Return string "Unknown" in case
CONFIG_ARM64_SSBD is disabled or arch workaround2 is not available
in the firmware.

Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 arch/arm64/kernel/cpu_errata.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 8469d3be7b15..8b60aa30a3fa 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -744,4 +744,24 @@ ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
 	return sprintf(buf, "Not affected\n");
 }
 
+ssize_t cpu_show_spec_store_bypass(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	switch (arm64_get_ssbd_state()) {
+	case ARM64_SSBD_MITIGATED:
+		return sprintf(buf, "Not affected\n");
+
+	case ARM64_SSBD_KERNEL:
+	case ARM64_SSBD_FORCE_ENABLE:
+		return sprintf(buf,
+			"Mitigation: Speculative Store Bypass disabled");
+
+	case ARM64_SSBD_FORCE_DISABLE:
+		return sprintf(buf, "Vulnerable\n");
+
+	default: /* ARM64_SSBD_UNKNOWN*/
+		return sprintf(buf, "Unknown\n");
+	}
+}
+
 #endif
-- 
2.11.0

[PATCH RESEND 6/6] arm64: enable generic CPU vulnerabilites support

[Mian Yousaf Kaukab]

Enable CPU vulnerabilty show functions for spectre_v1, spectre_v2,
meltdown and store-bypass.

Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0dec01a0c81c..ffd97bc0f5d5 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -84,6 +84,7 @@ config ARM64
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_CLOCKEVENTS_BROADCAST
 	select GENERIC_CPU_AUTOPROBE
+	select GENERIC_CPU_VULNERABILITIES
 	select GENERIC_EARLY_IOREMAP
 	select GENERIC_IDLE_POLL_SETUP
 	select GENERIC_IRQ_MULTI_HANDLER
-- 
2.11.0

Re: [PATCH RESEND 0/6] arm64: add support for generic cpu vulnerabilities

[Mian Yousaf Kaukab]

On Mon, Aug 27, 2018 at 04:33:04PM +0200, Mian Yousaf Kaukab wrote:
> GENERIC_CPU_VULNERABILITIES provide a common way to figure out if a
> system is affected by vulnerabilities like meltdown and other variants
> of spectre. This small series adds support for it in arm64.

Marc, Will, Can you please review this series?
Please let me know if I should rebase it against arm64 tree.

Thanks,
Yousaf

Re: [PATCH RESEND 2/6] arm64: add sysfs vulnerability show for meltdown

[Will Deacon]

On Mon, Aug 27, 2018 at 04:33:06PM +0200, Mian Yousaf Kaukab wrote:
> Checking CSV3 support directly in case CONFIG_UNMAP_KERNEL_AT_EL0
> is not enabled.
> 
> Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
> ---
>  arch/arm64/kernel/cpu_errata.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index dec10898d688..996edb4e18ad 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -22,6 +22,7 @@
>  #include <asm/cpu.h>
>  #include <asm/cputype.h>
>  #include <asm/cpufeature.h>
> +#include <asm/mmu.h>
>  
>  static bool __maybe_unused
>  is_affected_midr_range(const struct arm64_cpu_capabilities *entry, int scope)
> @@ -683,3 +684,26 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
>  	{
>  	}
>  };
> +
> +#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
> +
> +ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr,
> +		char *buf)
> +{
> +	u64 pfr0;
> +	u32 csv3;
> +
> +	if (arm64_kernel_unmapped_at_el0())
> +		return sprintf(buf, "Mitigation: KPTI\n");
> +
> +	pfr0 = read_cpuid(ID_AA64PFR0_EL1);
> +	csv3 = cpuid_feature_extract_unsigned_field(pfr0,
> +			ID_AA64PFR0_CSV3_SHIFT);
> +
> +	if (csv3 || is_cpu_meltdown_safe())
> +		return sprintf(buf, "Not affected\n");
> +
> +	return sprintf(buf, "Vulnerable\n");

This should say something like "Unknown", since we don't actually have a
reliable way to determine that a CPU is vulnerable. That's also a large
part of the reason why we haven't bothered implementing the sysfs interface
so far.

Will

Re: [PATCH RESEND 4/6] arm64: add sysfs vulnerability show for spectre v2

[Will Deacon]

On Mon, Aug 27, 2018 at 04:33:08PM +0200, Mian Yousaf Kaukab wrote:
> Only report mitigation present if hardening callback has been
> successfully installed.
> 
> Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
> ---
>  arch/arm64/kernel/cpu_errata.c | 34 +++++++++++++++++++++++++++++++++-
>  1 file changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index 92616431ae4e..8469d3be7b15 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -481,7 +481,8 @@ multi_entry_cap_cpu_enable(const struct arm64_cpu_capabilities *entry)
>  			caps->cpu_enable(caps);
>  }
>  
> -#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
> +#if defined(CONFIG_HARDEN_BRANCH_PREDICTOR) || \
> +	defined(CONFIG_GENERIC_CPU_VULNERABILITIES)
>  
>  /*
>   * List of CPUs where we need to issue a psci call to
> @@ -712,4 +713,35 @@ ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr,
>  	return sprintf(buf, "Mitigation: __user pointer sanitization\n");
>  }
>  
> +ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
> +		char *buf)
> +{
> +	u64 pfr0;
> +	struct bp_hardening_data *data;
> +
> +	pfr0 = read_cpuid(ID_AA64PFR0_EL1);
> +	if (cpuid_feature_extract_unsigned_field(pfr0, ID_AA64PFR0_CSV2_SHIFT))
> +		return sprintf(buf, "Not affected\n");

This strikes me as a pretty terrible interface, as it means that the file
can return different contents depending on which CPU it was read from on a
big/little machine. I think we need to either expose this per-cpu, or expose
the value of the system (e.g. if one CPU is vulnerable, we always say
vulnerable).

> +
> +	if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR)) {
> +		/*
> +		 * Hardware is vulnerable. Lets check if bp hardening callback
> +		 * has been successfully installed
> +		 */
> +		data = arm64_get_bp_hardening_data();

Related to the above, but this is accessing per-cpu stuff.

Will

Re: [PATCH RESEND 5/6] arm64: add sysfs vulnerability show for speculative store bypass

[Will Deacon]

On Mon, Aug 27, 2018 at 04:33:09PM +0200, Mian Yousaf Kaukab wrote:
> Return status based no ssbd_state. Return string "Unknown" in case
> CONFIG_ARM64_SSBD is disabled or arch workaround2 is not available
> in the firmware.
> 
> Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
> ---
>  arch/arm64/kernel/cpu_errata.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index 8469d3be7b15..8b60aa30a3fa 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -744,4 +744,24 @@ ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
>  	return sprintf(buf, "Not affected\n");
>  }
>  
> +ssize_t cpu_show_spec_store_bypass(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	switch (arm64_get_ssbd_state()) {
> +	case ARM64_SSBD_MITIGATED:
> +		return sprintf(buf, "Not affected\n");
> +
> +	case ARM64_SSBD_KERNEL:
> +	case ARM64_SSBD_FORCE_ENABLE:
> +		return sprintf(buf,
> +			"Mitigation: Speculative Store Bypass disabled");
> +
> +	case ARM64_SSBD_FORCE_DISABLE:
> +		return sprintf(buf, "Vulnerable\n");
> +
> +	default: /* ARM64_SSBD_UNKNOWN*/
> +		return sprintf(buf, "Unknown\n");
> +	}
> +}

This probably wants extending for CPUs that support SSBS (see
for-next/core).

Will

Re: [PATCH RESEND 0/6] arm64: add support for generic cpu vulnerabilities

[Will Deacon]

On Wed, Sep 05, 2018 at 11:25:33AM +0200, Mian Yousaf Kaukab wrote:
> On Mon, Aug 27, 2018 at 04:33:04PM +0200, Mian Yousaf Kaukab wrote:
> > GENERIC_CPU_VULNERABILITIES provide a common way to figure out if a
> > system is affected by vulnerabilities like meltdown and other variants
> > of spectre. This small series adds support for it in arm64.
> 
> Marc, Will, Can you please review this series?

Sorry it took so long to get to this, it's just consistently failed to
get to the top of my review queue. I had a quick look just now and there
are a few things to address before we can take the series.

Cheers,

Will

Re: [PATCH RESEND 3/6] arm64: add sysfs vulnerability show for spectre v1

[Robert Richter]

On 27.08.18 16:33:07, Mian Yousaf Kaukab wrote:
> Hard-coded since patches are merged and there are no configuration
> options.

Could you add a list of upstream patches to the description that are
required to solve this? This would be a strict definition for the
mitigation being enabled and makes it easier to check if backports are
affected or not. A build-time check would be ideal (e.g. checking for
certain macros).

Looking at arm64/kpti I see the following patches:

f84a56f73ddd^..f3804203306e 669474e772b9^..91b2d3442f6a

v4.16-rc1  f84a56f73ddd Documentation: Document array_index_nospec
v4.16-rc1  f3804203306e array_index_nospec: Sanitize speculative array de-references
v4.16-rc1  669474e772b9 arm64: barrier: Add CSDB macros to control data-value prediction
v4.16-rc1  022620eed3d0 arm64: Implement array_index_mask_nospec()
v4.16-rc1  51369e398d0d arm64: Make USER_DS an inclusive limit
v4.16-rc1  4d8efc2d5ee4 arm64: Use pointer masking to limit uaccess speculation
v4.16-rc1  6314d90e6493 arm64: entry: Ensure branch through syscall table is bounded under speculation
v4.16-rc1  c2f0ad4fc089 arm64: uaccess: Prevent speculative use of the current addr_limit
v4.16-rc1  84624087dd7e arm64: uaccess: Don't bother eliding access_ok checks in __{get, put}_user
v4.16-rc1  f71c2ffcb20d arm64: uaccess: Mask __user pointers for __arch_{clear, copy_*}_user
v4.16-rc1  91b2d3442f6a arm64: futex: Mask __user pointers prior to dereference

-Robert

> 
> Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
> ---
>  arch/arm64/kernel/cpu_errata.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index 996edb4e18ad..92616431ae4e 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -706,4 +706,10 @@ ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr,
>         return sprintf(buf, "Vulnerable\n");
>  }
> 
> +ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr,
> +               char *buf)
> +{
> +       return sprintf(buf, "Mitigation: __user pointer sanitization\n");
> +}
> +
>  #endif
> --
> 2.11.0
> 

Re: [PATCH RESEND 3/6] arm64: add sysfs vulnerability show for spectre v1

[Will Deacon]

On Mon, Sep 17, 2018 at 07:22:07PM +0200, Robert Richter wrote:
> On 27.08.18 16:33:07, Mian Yousaf Kaukab wrote:
> > Hard-coded since patches are merged and there are no configuration
> > options.
> 
> Could you add a list of upstream patches to the description that are
> required to solve this? This would be a strict definition for the
> mitigation being enabled and makes it easier to check if backports are
> affected or not. A build-time check would be ideal (e.g. checking for
> certain macros).

Hmm, I don't grok what you're proposing here. Why do we need a build-time
check (and to check what?)

Confused,

Will

Re: [PATCH RESEND 3/6] arm64: add sysfs vulnerability show for spectre v1

[Robert Richter]

On 18.09.18 09:38:05, Will Deacon wrote:
> On Mon, Sep 17, 2018 at 07:22:07PM +0200, Robert Richter wrote:
> > On 27.08.18 16:33:07, Mian Yousaf Kaukab wrote:
> > > Hard-coded since patches are merged and there are no configuration
> > > options.
> >
> > Could you add a list of upstream patches to the description that are
> > required to solve this? This would be a strict definition for the
> > mitigation being enabled and makes it easier to check if backports are
> > affected or not. A build-time check would be ideal (e.g. checking for
> > certain macros).
> 
> Hmm, I don't grok what you're proposing here. Why do we need a build-time
> check (and to check what?)

My concern is, that for kernel backports (esp. distro kernels) there
could be various interpretations of what "Mitigation: __user pointer
sanitization" means. So a list of upstream patches that need to be
backported in addition to this patch as a requirement would be good to
agree on. That should be documented in the patch description.

If these mitigations are available in a kernel backport, that could be
even checked at build time. E.g. we could have a sanity check if the
macro array_index_nospec() is defined. But such a check does not
replace a code review of a kernel backport.

I hope that makes sense?

-Robert

Re: [PATCH RESEND 3/6] arm64: add sysfs vulnerability show for spectre v1

[Will Deacon]

On Tue, Sep 18, 2018 at 11:52:27AM +0200, Robert Richter wrote:
> On 18.09.18 09:38:05, Will Deacon wrote:
> > On Mon, Sep 17, 2018 at 07:22:07PM +0200, Robert Richter wrote:
> > > On 27.08.18 16:33:07, Mian Yousaf Kaukab wrote:
> > > > Hard-coded since patches are merged and there are no configuration
> > > > options.
> > >
> > > Could you add a list of upstream patches to the description that are
> > > required to solve this? This would be a strict definition for the
> > > mitigation being enabled and makes it easier to check if backports are
> > > affected or not. A build-time check would be ideal (e.g. checking for
> > > certain macros).
> > 
> > Hmm, I don't grok what you're proposing here. Why do we need a build-time
> > check (and to check what?)
> 
> My concern is, that for kernel backports (esp. distro kernels) there
> could be various interpretations of what "Mitigation: __user pointer
> sanitization" means. So a list of upstream patches that need to be
> backported in addition to this patch as a requirement would be good to
> agree on. That should be documented in the patch description.
> 
> If these mitigations are available in a kernel backport, that could be
> even checked at build time. E.g. we could have a sanity check if the
> macro array_index_nospec() is defined. But such a check does not
> replace a code review of a kernel backport.
> 
> I hope that makes sense?

Ok, I see what you mean now, thanks. However, it doesn't sound much
different than backporting a patch with dependencies, so I'd rather
avoid adding additional code to treat this case specially.

Will

Re: [PATCH RESEND 3/6] arm64: add sysfs vulnerability show for spectre v1

[Robert Richter]

On 18.09.18 18:15:51, Will Deacon wrote:
> On Tue, Sep 18, 2018 at 11:52:27AM +0200, Robert Richter wrote:
> > On 18.09.18 09:38:05, Will Deacon wrote:
> > > On Mon, Sep 17, 2018 at 07:22:07PM +0200, Robert Richter wrote:
> > > > On 27.08.18 16:33:07, Mian Yousaf Kaukab wrote:
> > > > > Hard-coded since patches are merged and there are no configuration
> > > > > options.
> > > >
> > > > Could you add a list of upstream patches to the description that are
> > > > required to solve this? This would be a strict definition for the
> > > > mitigation being enabled and makes it easier to check if backports are
> > > > affected or not. A build-time check would be ideal (e.g. checking for
> > > > certain macros).
> > >
> > > Hmm, I don't grok what you're proposing here. Why do we need a build-time
> > > check (and to check what?)
> >
> > My concern is, that for kernel backports (esp. distro kernels) there
> > could be various interpretations of what "Mitigation: __user pointer
> > sanitization" means. So a list of upstream patches that need to be
> > backported in addition to this patch as a requirement would be good to
> > agree on. That should be documented in the patch description.
> >
> > If these mitigations are available in a kernel backport, that could be
> > even checked at build time. E.g. we could have a sanity check if the
> > macro array_index_nospec() is defined. But such a check does not
> > replace a code review of a kernel backport.
> >
> > I hope that makes sense?
> 
> Ok, I see what you mean now, thanks. However, it doesn't sound much
> different than backporting a patch with dependencies, so I'd rather
> avoid adding additional code to treat this case specially.

A pointer to the patches would be helpful as the dependencies are not
obvious. This is different to just backport a complete series of
patches.

-Robert

Re: [PATCH RESEND 0/6] arm64: add support for generic cpu vulnerabilities

[Mian Yousaf Kaukab]

On Mon, Sep 17, 2018 at 02:35:08PM +0100, Will Deacon wrote:
> On Wed, Sep 05, 2018 at 11:25:33AM +0200, Mian Yousaf Kaukab wrote:
> > On Mon, Aug 27, 2018 at 04:33:04PM +0200, Mian Yousaf Kaukab wrote:
> > > GENERIC_CPU_VULNERABILITIES provide a common way to figure out if a
> > > system is affected by vulnerabilities like meltdown and other variants
> > > of spectre. This small series adds support for it in arm64.
> > 
> > Marc, Will, Can you please review this series?
> 
> Sorry it took so long to get to this, it's just consistently failed to
> get to the top of my review queue. I had a quick look just now and there
> are a few things to address before we can take the series.
Thank you for the review. I will get back to you after fixing the comments as soon as possible.

> 
> Cheers,
> 
> Will

Thanks,
Yousaf