| Message ID | 20220112211258.21115-8-chang.seok.bae@intel.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | x86: Support Key Locker | expand |
On Wed, Jan 12, 2022 at 1:21 PM Chang S. Bae <chang.seok.bae@intel.com> wrote: > > The Internal Wrapping Key (IWKey) is an entity of Key Locker to encode a > clear text key into a key handle. This key is a pivot in protecting user > keys. So the value has to be randomized before being loaded in the > software-invisible CPU state. > > IWKey needs to be established before the first user. Given that the only > proposed Linux use case for Key Locker is dm-crypt, the feature could be > lazily enabled when the first dm-crypt user arrives, but there is no > precedent for late enabling of CPU features and it adds maintenance burden > without demonstrative benefit outside of minimizing the visibility of > Key Locker to userspace. > > The kernel generates random bytes and load them at boot time. These bytes > are flushed out immediately. > > Setting the CR4.KL bit does not always enable the feature so ensure the > dynamic CPU bit (CPUID.AESKLE) is set before loading the key. > > Given that the Linux Key Locker support is only intended for bare metal > dm-crypt consumption, and that switching IWKey per VM is untenable, > explicitly skip Key Locker setup in the X86_FEATURE_HYPERVISOR case. > > Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> > Reviewed-by: Dan Williams <dan.j.williams@intel.com> > Cc: x86@kernel.org > Cc: linux-kernel@vger.kernel.org > --- > Changes from RFC v2: > * Make bare metal only. > * Clean up the code (e.g. dynamically allocate the key cache). > (Dan Williams) > * Massage the changelog. > * Move out the LOADIWKEY wrapper and the Key Locker CPUID defines. > > Note, Dan wonders that given that the only proposed Linux use case for > Key Locker is dm-crypt, the feature could be lazily enabled when the > first dm-crypt user arrives, but as Dave notes there is no precedent > for late enabling of CPU features and it adds maintenance burden > without demonstrative benefit outside of minimizing the visibility of > Key Locker to userspace. > --- > arch/x86/include/asm/keylocker.h | 9 ++++ > arch/x86/kernel/Makefile | 1 + > arch/x86/kernel/cpu/common.c | 5 +- > arch/x86/kernel/keylocker.c | 79 ++++++++++++++++++++++++++++++++ > arch/x86/kernel/smpboot.c | 2 + > 5 files changed, 95 insertions(+), 1 deletion(-) > create mode 100644 arch/x86/kernel/keylocker.c > > diff --git a/arch/x86/include/asm/keylocker.h b/arch/x86/include/asm/keylocker.h > index e85dfb6c1524..820ac29c06d9 100644 > --- a/arch/x86/include/asm/keylocker.h > +++ b/arch/x86/include/asm/keylocker.h > @@ -5,6 +5,7 @@ > > #ifndef __ASSEMBLY__ > > +#include <asm/processor.h> > #include <linux/bits.h> > #include <asm/fpu/types.h> > > @@ -28,5 +29,13 @@ struct iwkey { > #define KEYLOCKER_CPUID_EBX_WIDE BIT(2) > #define KEYLOCKER_CPUID_EBX_BACKUP BIT(4) > > +#ifdef CONFIG_X86_KEYLOCKER > +void setup_keylocker(struct cpuinfo_x86 *c); > +void destroy_keylocker_data(void); > +#else > +#define setup_keylocker(c) do { } while (0) > +#define destroy_keylocker_data() do { } while (0) > +#endif > + > #endif /*__ASSEMBLY__ */ > #endif /* _ASM_KEYLOCKER_H */ > diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile > index 2ff3e600f426..e15efa238497 100644 > --- a/arch/x86/kernel/Makefile > +++ b/arch/x86/kernel/Makefile > @@ -144,6 +144,7 @@ obj-$(CONFIG_PERF_EVENTS) += perf_regs.o > obj-$(CONFIG_TRACING) += tracepoint.o > obj-$(CONFIG_SCHED_MC_PRIO) += itmt.o > obj-$(CONFIG_X86_UMIP) += umip.o > +obj-$(CONFIG_X86_KEYLOCKER) += keylocker.o > > obj-$(CONFIG_UNWINDER_ORC) += unwind_orc.o > obj-$(CONFIG_UNWINDER_FRAME_POINTER) += unwind_frame.o > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > index 0083464de5e3..23b4aa437c1e 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -57,6 +57,8 @@ > #include <asm/microcode_intel.h> > #include <asm/intel-family.h> > #include <asm/cpu_device_id.h> > +#include <asm/keylocker.h> > + > #include <asm/uv/uv.h> > #include <asm/sigframe.h> > > @@ -1595,10 +1597,11 @@ static void identify_cpu(struct cpuinfo_x86 *c) > /* Disable the PN if appropriate */ > squash_the_stupid_serial_number(c); > > - /* Set up SMEP/SMAP/UMIP */ > + /* Setup various Intel-specific CPU security features */ > setup_smep(c); > setup_smap(c); > setup_umip(c); > + setup_keylocker(c); > > /* Enable FSGSBASE instructions if available. */ > if (cpu_has(c, X86_FEATURE_FSGSBASE)) { > diff --git a/arch/x86/kernel/keylocker.c b/arch/x86/kernel/keylocker.c > new file mode 100644 > index 000000000000..87d775a65716 > --- /dev/null > +++ b/arch/x86/kernel/keylocker.c > @@ -0,0 +1,79 @@ > +// SPDX-License-Identifier: GPL-2.0-only > + > +/* > + * Setup Key Locker feature and support internal wrapping key > + * management. > + */ > + > +#include <linux/random.h> > +#include <linux/poison.h> > + > +#include <asm/fpu/api.h> > +#include <asm/keylocker.h> > +#include <asm/tlbflush.h> > + > +static __initdata struct keylocker_setup_data { > + struct iwkey key; > +} kl_setup; > + > +static void __init generate_keylocker_data(void) > +{ > + get_random_bytes(&kl_setup.key.integrity_key, sizeof(kl_setup.key.integrity_key)); > + get_random_bytes(&kl_setup.key.encryption_key, sizeof(kl_setup.key.encryption_key)); > +} > + > +void __init destroy_keylocker_data(void) > +{ > + memset(&kl_setup.key, KEY_DESTROY, sizeof(kl_setup.key)); > +} > + > +static void __init load_keylocker(void) I am late to this party by 6 months, but: load_keylocker() cannot be __init, as it gets called during SMP core onlining.
On Wed, Aug 24, 2022 at 3:21 PM Chang S. Bae <chang.seok.bae@intel.com> wrote: > > On 8/23/2022 8:49 AM, Evan Green wrote: > > On Wed, Jan 12, 2022 at 1:21 PM Chang S. Bae <chang.seok.bae@intel.com> wrote: > >> > <snip> > >> + > >> +static void __init load_keylocker(void) > > > > I am late to this party by 6 months, but: > > load_keylocker() cannot be __init, as it gets called during SMP core onlining. > > Yeah, it looks like the case with this patch only. > > But the next patch [1] limits the call during boot time only: > > if (c == &boot_cpu_data) { > ... > load_keylocker(); > ... > } else { > ... > if (!kl_setup.initialized) { > load_keylocker(); > } else if (valid_kl) { > rc = copy_keylocker(); > ... > } > } > > kl_setup.initialized is set by native_smp_cpus_done() -> > destroy_keylocker_data() when CPUs are booted. Then load_keylocker() is > not called because the root key (aka IWKey) is no longer available in > memory. > > Now this 'valid_kl' flag should be always on unless the root key backup > is corrupted. Then copy_keylocker() loads the root key from the backup > in the platform state. > > So I think the onlining CPU won't call it. > > Maybe this bit can be much clarified in a separate (new) patch, instead > of being part of another like [1]. Whatever we ended up landing in the ChromeOS tree (which I think was v4 of this series) actively hit this bug in hibernation, which is how I found it. I couldn't get a full backtrace because the backtracing code tripped over itself as well for some reason. If the next patch in this series is different from what we landed in ChromeOS, then maybe your description is correct, but I haven't dug in to understand the delta. -Evan
On 8/25/2022 8:31 AM, Evan Green wrote: > > Here's the log I've got that pointed me down this path: > https://pastebin.com/VvR1EHvE <3>[43486.261583] x86/keylocker: The key backup access failed with read error. <3>[43486.261584] x86/keylocker: Failed to restore internal wrapping key. Looks like the IWKey backup was corrupted on that system. > Relevant bit pasted below: > > <6>[43486.263035] Enabling non-boot CPUs ... > <6>[43486.263081] x86: Booting SMP configuration: > <6>[43486.263082] smpboot: Booting Node 0 Processor 1 APIC 0x1 > <2>[43486.264010] kernel tried to execute NX-protected page - exploit > attempt? (uid: 0) > <1>[43486.264019] BUG: unable to handle page fault for address: ffffffff94b483a6 > <1>[43486.264021] #PF: supervisor instruction fetch in kernel mode > <1>[43486.264023] #PF: error_code(0x0011) - permissions violation > <6>[43486.264025] PGD 391c0e067 P4D 391c0e067 PUD 391c0f063 PMD > 10006c063 PTE 8000000392148163 > <4>[43486.264031] Oops: 0011 [#1] PREEMPT SMP NOPTI > <4>[43486.264035] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G U > 5.10.136-19391-gadfe4d4b8c04 #1 > b640352a7a0e5f1522aed724296ad63f90c007df > <4>[43486.264036] Hardware name: Google Primus/Primus, BIOS > Google_Primus.14505.145.0 06/23/2022 > <4>[43486.264042] RIP: 0010:load_keylocker+0x0/0x7f But, I don't get the reason why it hit this. On the wake-up path, copy_keylocker() is supposed to be called. I added some printout in there, and it looks to be fine with me: [ 218.488711] Enabling non-boot CPUs ... [ 218.488794] x86: Booting SMP configuration: [ 218.488795] smpboot: Booting Node 0 Processor 1 APIC 0x1 [ 218.490634] x86/keylocker: restore processor (id=1) [ 218.491186] CPU1 is up ... Thanks, Chang
On Wed, Aug 31, 2022 at 4:16 PM Chang S. Bae <chang.seok.bae@intel.com> wrote: > > On 8/25/2022 8:31 AM, Evan Green wrote: > > > > Here's the log I've got that pointed me down this path: > > https://pastebin.com/VvR1EHvE > > <3>[43486.261583] x86/keylocker: The key backup access failed with > read error. > <3>[43486.261584] x86/keylocker: Failed to restore internal > wrapping key. > > Looks like the IWKey backup was corrupted on that system. > > > Relevant bit pasted below: > > > > <6>[43486.263035] Enabling non-boot CPUs ... > > <6>[43486.263081] x86: Booting SMP configuration: > > <6>[43486.263082] smpboot: Booting Node 0 Processor 1 APIC 0x1 > > <2>[43486.264010] kernel tried to execute NX-protected page - exploit > > attempt? (uid: 0) > > <1>[43486.264019] BUG: unable to handle page fault for address: ffffffff94b483a6 > > <1>[43486.264021] #PF: supervisor instruction fetch in kernel mode > > <1>[43486.264023] #PF: error_code(0x0011) - permissions violation > > <6>[43486.264025] PGD 391c0e067 P4D 391c0e067 PUD 391c0f063 PMD > > 10006c063 PTE 8000000392148163 > > <4>[43486.264031] Oops: 0011 [#1] PREEMPT SMP NOPTI > > <4>[43486.264035] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G U > > 5.10.136-19391-gadfe4d4b8c04 #1 > > b640352a7a0e5f1522aed724296ad63f90c007df > > <4>[43486.264036] Hardware name: Google Primus/Primus, BIOS > > Google_Primus.14505.145.0 06/23/2022 > > <4>[43486.264042] RIP: 0010:load_keylocker+0x0/0x7f > > But, I don't get the reason why it hit this. On the wake-up path, > copy_keylocker() is supposed to be called. Interesting, that's helpful. I thought I had a lead based on this, which was that in this case we were doing a hibernate to shutdown, rather than hibernate to S4. The IWKey backup is only valid down to S4, so a read error on resume from this type of hibernate might make sense. I know keylocker won't successfully maintain handles across a hibernate to shutdown and subsequent resume, but it shouldn't crash either. But this still doesn't explain this crash, since in this case we're still on our way down and haven't even done the shutdown yet. We can see the "PM: hibernation: Image created (1536412 pages copied)" log line just before the keylocker read failure. So then it seems something's not working with the pre-hibernate CPU hotplug path? > > I added some printout in there, and it looks to be fine with me: > > [ 218.488711] Enabling non-boot CPUs ... > [ 218.488794] x86: Booting SMP configuration: > [ 218.488795] smpboot: Booting Node 0 Processor 1 APIC 0x1 > [ 218.490634] x86/keylocker: restore processor (id=1) > [ 218.491186] CPU1 is up > ... How were you exercising the CPU onlining in this case? Boot, cpu hotplug, or hibernate? -Evan
On 9/6/2022 9:22 AM, Evan Green wrote: > On Wed, Aug 31, 2022 at 4:16 PM Chang S. Bae <chang.seok.bae@intel.com> wrote: > > But this still doesn't explain this crash, since in this case we're > still on our way down and haven't even done the shutdown yet. We can > see the "PM: hibernation: Image created (1536412 pages copied)" log > line just before the keylocker read failure. So then it seems > something's not working with the pre-hibernate CPU hotplug path? No, that backup crash message came from the boot-CPU's wakeup path: __restore_processor_state()->restore_keylocker(). If the issue is repeatable, then I suspect that's something to do with the specific platform implementation. I don't have any detail yet on the customized systems. Let me check with some Chrome HW folks. > How were you exercising the CPU onlining in this case? Boot, cpu > hotplug, or hibernate? Hibernate. Thanks, Chang
diff --git a/arch/x86/include/asm/keylocker.h b/arch/x86/include/asm/keylocker.h index e85dfb6c1524..820ac29c06d9 100644 --- a/arch/x86/include/asm/keylocker.h +++ b/arch/x86/include/asm/keylocker.h @@ -5,6 +5,7 @@ #ifndef __ASSEMBLY__ +#include <asm/processor.h> #include <linux/bits.h> #include <asm/fpu/types.h> @@ -28,5 +29,13 @@ struct iwkey { #define KEYLOCKER_CPUID_EBX_WIDE BIT(2) #define KEYLOCKER_CPUID_EBX_BACKUP BIT(4) +#ifdef CONFIG_X86_KEYLOCKER +void setup_keylocker(struct cpuinfo_x86 *c); +void destroy_keylocker_data(void); +#else +#define setup_keylocker(c) do { } while (0) +#define destroy_keylocker_data() do { } while (0) +#endif + #endif /*__ASSEMBLY__ */ #endif /* _ASM_KEYLOCKER_H */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 2ff3e600f426..e15efa238497 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -144,6 +144,7 @@ obj-$(CONFIG_PERF_EVENTS) += perf_regs.o obj-$(CONFIG_TRACING) += tracepoint.o obj-$(CONFIG_SCHED_MC_PRIO) += itmt.o obj-$(CONFIG_X86_UMIP) += umip.o +obj-$(CONFIG_X86_KEYLOCKER) += keylocker.o obj-$(CONFIG_UNWINDER_ORC) += unwind_orc.o obj-$(CONFIG_UNWINDER_FRAME_POINTER) += unwind_frame.o diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 0083464de5e3..23b4aa437c1e 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -57,6 +57,8 @@ #include <asm/microcode_intel.h> #include <asm/intel-family.h> #include <asm/cpu_device_id.h> +#include <asm/keylocker.h> + #include <asm/uv/uv.h> #include <asm/sigframe.h> @@ -1595,10 +1597,11 @@ static void identify_cpu(struct cpuinfo_x86 *c) /* Disable the PN if appropriate */ squash_the_stupid_serial_number(c); - /* Set up SMEP/SMAP/UMIP */ + /* Setup various Intel-specific CPU security features */ setup_smep(c); setup_smap(c); setup_umip(c); + setup_keylocker(c); /* Enable FSGSBASE instructions if available. */ if (cpu_has(c, X86_FEATURE_FSGSBASE)) { diff --git a/arch/x86/kernel/keylocker.c b/arch/x86/kernel/keylocker.c new file mode 100644 index 000000000000..87d775a65716 --- /dev/null +++ b/arch/x86/kernel/keylocker.c @@ -0,0 +1,79 @@ +// SPDX-License-Identifier: GPL-2.0-only + +/* + * Setup Key Locker feature and support internal wrapping key + * management. + */ + +#include <linux/random.h> +#include <linux/poison.h> + +#include <asm/fpu/api.h> +#include <asm/keylocker.h> +#include <asm/tlbflush.h> + +static __initdata struct keylocker_setup_data { + struct iwkey key; +} kl_setup; + +static void __init generate_keylocker_data(void) +{ + get_random_bytes(&kl_setup.key.integrity_key, sizeof(kl_setup.key.integrity_key)); + get_random_bytes(&kl_setup.key.encryption_key, sizeof(kl_setup.key.encryption_key)); +} + +void __init destroy_keylocker_data(void) +{ + memset(&kl_setup.key, KEY_DESTROY, sizeof(kl_setup.key)); +} + +static void __init load_keylocker(void) +{ + kernel_fpu_begin(); + load_xmm_iwkey(&kl_setup.key); + kernel_fpu_end(); +} + +/** + * setup_keylocker - Enable the feature. + * @c: A pointer to struct cpuinfo_x86 + */ +void __ref setup_keylocker(struct cpuinfo_x86 *c) +{ + /* This feature is not compatible with a hypervisor. */ + if (!cpu_feature_enabled(X86_FEATURE_KEYLOCKER) || + cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) + goto out; + + cr4_set_bits(X86_CR4_KEYLOCKER); + + if (c == &boot_cpu_data) { + u32 eax, ebx, ecx, edx; + + cpuid_count(KEYLOCKER_CPUID, 0, &eax, &ebx, &ecx, &edx); + /* + * Check the feature readiness via CPUID. Note that the + * CPUID AESKLE bit is conditionally set only when CR4.KL + * is set. + */ + if (!(ebx & KEYLOCKER_CPUID_EBX_AESKLE) || + !(eax & KEYLOCKER_CPUID_EAX_SUPERVISOR)) { + pr_debug("x86/keylocker: Not fully supported.\n"); + goto disable; + } + + generate_keylocker_data(); + } + + load_keylocker(); + + pr_info_once("x86/keylocker: Enabled.\n"); + return; + +disable: + setup_clear_cpu_cap(X86_FEATURE_KEYLOCKER); + pr_info_once("x86/keylocker: Disabled.\n"); +out: + /* Make sure the feature disabled for kexec-reboot. */ + cr4_clear_bits(X86_CR4_KEYLOCKER); +} diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 617012f4619f..00cfa64948f5 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -82,6 +82,7 @@ #include <asm/spec-ctrl.h> #include <asm/hw_irq.h> #include <asm/stackprotector.h> +#include <asm/keylocker.h> #ifdef CONFIG_ACPI_CPPC_LIB #include <acpi/cppc_acpi.h> @@ -1489,6 +1490,7 @@ void __init native_smp_cpus_done(unsigned int max_cpus) nmi_selftest(); impress_friends(); mtrr_aps_init(); + destroy_keylocker_data(); } static int __initdata setup_possible_cpus = -1;