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SubjectRe: [PATCH v2 08/11] firmware: enable run time change of forcing fallback loader
On Fri, Feb 23, 2018 at 6:46 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> Currently one requires to test four kernel configurations to test the
> firmware API completely:
>
> 0)
> CONFIG_FW_LOADER=y
>
> 1)
> o CONFIG_FW_LOADER=y
> o CONFIG_FW_LOADER_USER_HELPER=y
>
> 2)
> o CONFIG_FW_LOADER=y
> o CONFIG_FW_LOADER_USER_HELPER=y
> o CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
>
> 3) When CONFIG_FW_LOADER=m the built-in stuff is disabled, we have
> no current tests for this.
>
> We can reduce the requirements to three kernel configurations by making
> fw_config.force_sysfs_fallback a proc knob we flip on off. For kernels that
> disable CONFIG_IKCONFIG_PROC this can also enable one to inspect if
> CONFIG_FW_LOADER_USER_HELPER_FALLBACK was enabled at build time by checking
> the proc value at boot time.

You'll still need compile tests of each configuration, but I love that
this will give one kernel to test them all.

Acked-by: Kees Cook <keescook@chromium.org>

-Kees


>
> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
> ---
> drivers/base/firmware_fallback.c | 1 +
> drivers/base/firmware_fallback.h | 4 +++-
> drivers/base/firmware_fallback_table.c | 17 +++++++++++++++++
> kernel/sysctl.c | 11 +++++++++++
> 4 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/firmware_fallback.c b/drivers/base/firmware_fallback.c
> index 47690207e0ee..cbce9a950cd8 100644
> --- a/drivers/base/firmware_fallback.c
> +++ b/drivers/base/firmware_fallback.c
> @@ -7,6 +7,7 @@
> #include <linux/security.h>
> #include <linux/highmem.h>
> #include <linux/umh.h>
> +#include <linux/sysctl.h>
>
> #include "firmware_fallback.h"
> #include "firmware_loader.h"
> diff --git a/drivers/base/firmware_fallback.h b/drivers/base/firmware_fallback.h
> index 550498c7fa4c..ca7e69a8417b 100644
> --- a/drivers/base/firmware_fallback.h
> +++ b/drivers/base/firmware_fallback.h
> @@ -12,12 +12,14 @@
> *
> * @force_sysfs_fallback: force the sysfs fallback mechanism to be used
> * as if one had enabled CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y.
> + * Useful to help debug a CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
> + * functionality on a kernel where that config entry has been disabled.
> * @old_timeout: for internal use
> * @loading_timeout: the timeout to wait for the fallback mechanism before
> * giving up, in seconds.
> */
> struct firmware_fallback_config {
> - const bool force_sysfs_fallback;
> + unsigned int force_sysfs_fallback;
> int old_timeout;
> int loading_timeout;
> };
> diff --git a/drivers/base/firmware_fallback_table.c b/drivers/base/firmware_fallback_table.c
> index 53cc4e492520..77300d5e9c52 100644
> --- a/drivers/base/firmware_fallback_table.c
> +++ b/drivers/base/firmware_fallback_table.c
> @@ -19,6 +19,9 @@
> /* Module or buit-in */
> #ifdef CONFIG_FW_LOADER_USER_HELPER
>
> +static unsigned int zero;
> +static unsigned int one = 1;
> +
> struct firmware_fallback_config fw_fallback_config = {
> .force_sysfs_fallback = IS_ENABLED(CONFIG_FW_LOADER_USER_HELPER_FALLBACK),
> .loading_timeout = 60,
> @@ -26,4 +29,18 @@ struct firmware_fallback_config fw_fallback_config = {
> };
> EXPORT_SYMBOL_GPL(fw_fallback_config);
>
> +struct ctl_table firmware_config_table[] = {
> + {
> + .procname = "force_sysfs_fallback",
> + .data = &fw_fallback_config.force_sysfs_fallback,
> + .maxlen = sizeof(unsigned int),
> + .mode = 0644,
> + .proc_handler = proc_douintvec_minmax,
> + .extra1 = &zero,
> + .extra2 = &one,
> + },
> + { }
> +};
> +EXPORT_SYMBOL_GPL(firmware_config_table);
> +
> #endif
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index acdf4e85c0a1..aa8355953fcf 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -253,6 +253,10 @@ extern struct ctl_table random_table[];
> extern struct ctl_table epoll_table[];
> #endif
>
> +#ifdef CONFIG_FW_LOADER_USER_HELPER
> +extern struct ctl_table firmware_config_table[];
> +#endif
> +
> #ifdef HAVE_ARCH_PICK_MMAP_LAYOUT
> int sysctl_legacy_va_layout;
> #endif
> @@ -748,6 +752,13 @@ static struct ctl_table kern_table[] = {
> .mode = 0555,
> .child = usermodehelper_table,
> },
> +#ifdef CONFIG_FW_LOADER_USER_HELPER
> + {
> + .procname = "firmware_config",
> + .mode = 0555,
> + .child = firmware_config_table,
> + },
> +#endif
> {
> .procname = "overflowuid",
> .data = &overflowuid,
> --
> 2.16.2
>



--
Kees Cook
Pixel Security

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