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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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