* [PATCH V34 14/29] ACPI: Limit access to custom_method when the kernel is locked down [not found] <20190622000358.19895-1-matthewgarrett@google.com> @ 2019-06-22 0:03 ` Matthew Garrett 2019-06-22 23:59 ` Kees Cook 2019-06-22 0:03 ` [PATCH V34 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett 2019-06-22 0:03 ` [PATCH V34 16/29] acpi: Disable ACPI table override if the kernel is " Matthew Garrett 2 siblings, 1 reply; 6+ messages in thread From: Matthew Garrett @ 2019-06-22 0:03 UTC (permalink / raw) To: jmorris Cc: linux-security-module, linux-kernel, linux-api, Matthew Garrett, Matthew Garrett, David Howells, linux-acpi From: Matthew Garrett <mjg59@srcf.ucam.org> custom_method effectively allows arbitrary access to system memory, making it possible for an attacker to circumvent restrictions on module loading. Disable it if the kernel is locked down. Signed-off-by: Matthew Garrett <mjg59@google.com> Signed-off-by: David Howells <dhowells@redhat.com> cc: linux-acpi@vger.kernel.org --- drivers/acpi/custom_method.c | 6 ++++++ include/linux/security.h | 1 + security/lockdown/lockdown.c | 1 + 3 files changed, 8 insertions(+) diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c index aa972dc5cb7e..6e56f9f43492 100644 --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -8,6 +8,7 @@ #include <linux/uaccess.h> #include <linux/debugfs.h> #include <linux/acpi.h> +#include <linux/security.h> #include "internal.h" @@ -28,6 +29,11 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, struct acpi_table_header table; acpi_status status; + int ret; + + ret = security_locked_down(LOCKDOWN_ACPI_TABLES); + if (ret) + return ret; if (!(*ppos)) { /* parse the table header to get the table length */ diff --git a/include/linux/security.h b/include/linux/security.h index 30bc6f058926..cc2b5ee4cadd 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -89,6 +89,7 @@ enum lockdown_reason { LOCKDOWN_PCI_ACCESS, LOCKDOWN_IOPORT, LOCKDOWN_MSR, + LOCKDOWN_ACPI_TABLES, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 297a065e6261..1725224f0024 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -25,6 +25,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_PCI_ACCESS] = "direct PCI access", [LOCKDOWN_IOPORT] = "raw io port access", [LOCKDOWN_MSR] = "raw MSR access", + [LOCKDOWN_ACPI_TABLES] = "modified ACPI tables", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", }; -- 2.22.0.410.gd8fdbe21b5-goog ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH V34 14/29] ACPI: Limit access to custom_method when the kernel is locked down 2019-06-22 0:03 ` [PATCH V34 14/29] ACPI: Limit access to custom_method when the kernel is locked down Matthew Garrett @ 2019-06-22 23:59 ` Kees Cook 0 siblings, 0 replies; 6+ messages in thread From: Kees Cook @ 2019-06-22 23:59 UTC (permalink / raw) To: Matthew Garrett Cc: jmorris, linux-security-module, linux-kernel, linux-api, Matthew Garrett, Matthew Garrett, David Howells, linux-acpi On Fri, Jun 21, 2019 at 05:03:43PM -0700, Matthew Garrett wrote: > From: Matthew Garrett <mjg59@srcf.ucam.org> > > custom_method effectively allows arbitrary access to system memory, making > it possible for an attacker to circumvent restrictions on module loading. > Disable it if the kernel is locked down. > > Signed-off-by: Matthew Garrett <mjg59@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > Signed-off-by: David Howells <dhowells@redhat.com> > cc: linux-acpi@vger.kernel.org > --- > drivers/acpi/custom_method.c | 6 ++++++ > include/linux/security.h | 1 + > security/lockdown/lockdown.c | 1 + > 3 files changed, 8 insertions(+) > > diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c > index aa972dc5cb7e..6e56f9f43492 100644 > --- a/drivers/acpi/custom_method.c > +++ b/drivers/acpi/custom_method.c > @@ -8,6 +8,7 @@ > #include <linux/uaccess.h> > #include <linux/debugfs.h> > #include <linux/acpi.h> > +#include <linux/security.h> > > #include "internal.h" > > @@ -28,6 +29,11 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, > > struct acpi_table_header table; > acpi_status status; > + int ret; > + > + ret = security_locked_down(LOCKDOWN_ACPI_TABLES); > + if (ret) > + return ret; > > if (!(*ppos)) { > /* parse the table header to get the table length */ > diff --git a/include/linux/security.h b/include/linux/security.h > index 30bc6f058926..cc2b5ee4cadd 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -89,6 +89,7 @@ enum lockdown_reason { > LOCKDOWN_PCI_ACCESS, > LOCKDOWN_IOPORT, > LOCKDOWN_MSR, > + LOCKDOWN_ACPI_TABLES, > LOCKDOWN_INTEGRITY_MAX, > LOCKDOWN_CONFIDENTIALITY_MAX, > }; > diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c > index 297a065e6261..1725224f0024 100644 > --- a/security/lockdown/lockdown.c > +++ b/security/lockdown/lockdown.c > @@ -25,6 +25,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { > [LOCKDOWN_PCI_ACCESS] = "direct PCI access", > [LOCKDOWN_IOPORT] = "raw io port access", > [LOCKDOWN_MSR] = "raw MSR access", > + [LOCKDOWN_ACPI_TABLES] = "modified ACPI tables", > [LOCKDOWN_INTEGRITY_MAX] = "integrity", > [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", > }; > -- > 2.22.0.410.gd8fdbe21b5-goog > -- Kees Cook ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH V34 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down [not found] <20190622000358.19895-1-matthewgarrett@google.com> 2019-06-22 0:03 ` [PATCH V34 14/29] ACPI: Limit access to custom_method when the kernel is locked down Matthew Garrett @ 2019-06-22 0:03 ` Matthew Garrett 2019-06-22 23:59 ` Kees Cook 2019-06-22 0:03 ` [PATCH V34 16/29] acpi: Disable ACPI table override if the kernel is " Matthew Garrett 2 siblings, 1 reply; 6+ messages in thread From: Matthew Garrett @ 2019-06-22 0:03 UTC (permalink / raw) To: jmorris Cc: linux-security-module, linux-kernel, linux-api, Josh Boyer, David Howells, Matthew Garrett, Dave Young, linux-acpi From: Josh Boyer <jwboyer@redhat.com> This option allows userspace to pass the RSDP address to the kernel, which makes it possible for a user to modify the workings of hardware . Reject the option when the kernel is locked down. Signed-off-by: Josh Boyer <jwboyer@redhat.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Matthew Garrett <mjg59@google.com> cc: Dave Young <dyoung@redhat.com> cc: linux-acpi@vger.kernel.org --- drivers/acpi/osl.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index f29e427d0d1d..60cda8a0f36b 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -40,6 +40,7 @@ #include <linux/list.h> #include <linux/jiffies.h> #include <linux/semaphore.h> +#include <linux/security.h> #include <asm/io.h> #include <linux/uaccess.h> @@ -194,7 +195,7 @@ acpi_physical_address __init acpi_os_get_root_pointer(void) acpi_physical_address pa; #ifdef CONFIG_KEXEC - if (acpi_rsdp) + if (acpi_rsdp && !security_locked_down(LOCKDOWN_ACPI_TABLES)) return acpi_rsdp; #endif pa = acpi_arch_get_root_pointer(); -- 2.22.0.410.gd8fdbe21b5-goog ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH V34 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down 2019-06-22 0:03 ` [PATCH V34 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett @ 2019-06-22 23:59 ` Kees Cook 0 siblings, 0 replies; 6+ messages in thread From: Kees Cook @ 2019-06-22 23:59 UTC (permalink / raw) To: Matthew Garrett Cc: jmorris, linux-security-module, linux-kernel, linux-api, Josh Boyer, David Howells, Matthew Garrett, Dave Young, linux-acpi On Fri, Jun 21, 2019 at 05:03:44PM -0700, Matthew Garrett wrote: > From: Josh Boyer <jwboyer@redhat.com> > > This option allows userspace to pass the RSDP address to the kernel, which > makes it possible for a user to modify the workings of hardware . Reject > the option when the kernel is locked down. > > Signed-off-by: Josh Boyer <jwboyer@redhat.com> Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > Signed-off-by: David Howells <dhowells@redhat.com> > Signed-off-by: Matthew Garrett <mjg59@google.com> > cc: Dave Young <dyoung@redhat.com> > cc: linux-acpi@vger.kernel.org > --- > drivers/acpi/osl.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c > index f29e427d0d1d..60cda8a0f36b 100644 > --- a/drivers/acpi/osl.c > +++ b/drivers/acpi/osl.c > @@ -40,6 +40,7 @@ > #include <linux/list.h> > #include <linux/jiffies.h> > #include <linux/semaphore.h> > +#include <linux/security.h> > > #include <asm/io.h> > #include <linux/uaccess.h> > @@ -194,7 +195,7 @@ acpi_physical_address __init acpi_os_get_root_pointer(void) > acpi_physical_address pa; > > #ifdef CONFIG_KEXEC > - if (acpi_rsdp) > + if (acpi_rsdp && !security_locked_down(LOCKDOWN_ACPI_TABLES)) > return acpi_rsdp; > #endif > pa = acpi_arch_get_root_pointer(); > -- > 2.22.0.410.gd8fdbe21b5-goog > -- Kees Cook ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH V34 16/29] acpi: Disable ACPI table override if the kernel is locked down [not found] <20190622000358.19895-1-matthewgarrett@google.com> 2019-06-22 0:03 ` [PATCH V34 14/29] ACPI: Limit access to custom_method when the kernel is locked down Matthew Garrett 2019-06-22 0:03 ` [PATCH V34 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett @ 2019-06-22 0:03 ` Matthew Garrett 2019-06-23 0:00 ` Kees Cook 2 siblings, 1 reply; 6+ messages in thread From: Matthew Garrett @ 2019-06-22 0:03 UTC (permalink / raw) To: jmorris Cc: linux-security-module, linux-kernel, linux-api, Linn Crosetto, David Howells, Matthew Garrett, linux-acpi From: Linn Crosetto <linn@hpe.com> From the kernel documentation (initrd_table_override.txt): If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible to override nearly any ACPI table provided by the BIOS with an instrumented, modified one. When lockdown is enabled, the kernel should disallow any unauthenticated changes to kernel space. ACPI tables contain code invoked by the kernel, so do not allow ACPI tables to be overridden if the kernel is locked down. Signed-off-by: Linn Crosetto <linn@hpe.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Matthew Garrett <mjg59@google.com> cc: linux-acpi@vger.kernel.org --- drivers/acpi/tables.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c index 8fccbe49612a..41d9ccd0e075 100644 --- a/drivers/acpi/tables.c +++ b/drivers/acpi/tables.c @@ -34,6 +34,7 @@ #include <linux/memblock.h> #include <linux/earlycpio.h> #include <linux/initrd.h> +#include <linux/security.h> #include "internal.h" #ifdef CONFIG_ACPI_CUSTOM_DSDT @@ -539,6 +540,11 @@ void __init acpi_table_upgrade(void) if (table_nr == 0) return; + if (security_locked_down(LOCKDOWN_ACPI_TABLES)) { + pr_notice("kernel is locked down, ignoring table override\n"); + return; + } + acpi_tables_addr = memblock_find_in_range(0, ACPI_TABLE_UPGRADE_MAX_PHYS, all_tables_size, PAGE_SIZE); -- 2.22.0.410.gd8fdbe21b5-goog ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH V34 16/29] acpi: Disable ACPI table override if the kernel is locked down 2019-06-22 0:03 ` [PATCH V34 16/29] acpi: Disable ACPI table override if the kernel is " Matthew Garrett @ 2019-06-23 0:00 ` Kees Cook 0 siblings, 0 replies; 6+ messages in thread From: Kees Cook @ 2019-06-23 0:00 UTC (permalink / raw) To: Matthew Garrett Cc: jmorris, linux-security-module, linux-kernel, linux-api, Linn Crosetto, David Howells, Matthew Garrett, linux-acpi On Fri, Jun 21, 2019 at 05:03:45PM -0700, Matthew Garrett wrote: > From: Linn Crosetto <linn@hpe.com> > > From the kernel documentation (initrd_table_override.txt): > > If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible > to override nearly any ACPI table provided by the BIOS with an > instrumented, modified one. > > When lockdown is enabled, the kernel should disallow any unauthenticated > changes to kernel space. ACPI tables contain code invoked by the kernel, > so do not allow ACPI tables to be overridden if the kernel is locked down. > > Signed-off-by: Linn Crosetto <linn@hpe.com> Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > Signed-off-by: David Howells <dhowells@redhat.com> > Signed-off-by: Matthew Garrett <mjg59@google.com> > cc: linux-acpi@vger.kernel.org > --- > drivers/acpi/tables.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c > index 8fccbe49612a..41d9ccd0e075 100644 > --- a/drivers/acpi/tables.c > +++ b/drivers/acpi/tables.c > @@ -34,6 +34,7 @@ > #include <linux/memblock.h> > #include <linux/earlycpio.h> > #include <linux/initrd.h> > +#include <linux/security.h> > #include "internal.h" > > #ifdef CONFIG_ACPI_CUSTOM_DSDT > @@ -539,6 +540,11 @@ void __init acpi_table_upgrade(void) > if (table_nr == 0) > return; > > + if (security_locked_down(LOCKDOWN_ACPI_TABLES)) { > + pr_notice("kernel is locked down, ignoring table override\n"); > + return; > + } > + > acpi_tables_addr = > memblock_find_in_range(0, ACPI_TABLE_UPGRADE_MAX_PHYS, > all_tables_size, PAGE_SIZE); > -- > 2.22.0.410.gd8fdbe21b5-goog > -- Kees Cook ^ permalink raw reply [flat|nested] 6+ messages in thread
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Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2019-06-22 0:03 ` [PATCH V34 14/29] ACPI: Limit access to custom_method when the kernel is locked down Matthew Garrett
2019-06-22 23:59 ` Kees Cook
2019-06-22 0:03 ` [PATCH V34 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett
2019-06-22 23:59 ` Kees Cook
2019-06-22 0:03 ` [PATCH V34 16/29] acpi: Disable ACPI table override if the kernel is " Matthew Garrett
2019-06-23 0:00 ` Kees Cook
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