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    SubjectRe: [PATCH v2 12/63] thermal: intel: int340x_thermal: Use struct_group() for memcpy() region
    On Wed, Aug 18, 2021 at 8:08 AM Kees Cook <keescook@chromium.org> wrote:
    >
    > In preparation for FORTIFY_SOURCE performing compile-time and run-time
    > field bounds checking for memcpy(), avoid intentionally writing across
    > neighboring fields.
    >
    > Use struct_group() in struct art around members weight, and ac[0-9]_max,
    > so they can be referenced together. This will allow memcpy() and sizeof()
    > to more easily reason about sizes, improve readability, and avoid future
    > warnings about writing beyond the end of weight.
    >
    > "pahole" shows no size nor member offset changes to struct art.
    > "objdump -d" shows no meaningful object code changes (i.e. only source
    > line number induced differences).
    >
    > Cc: Zhang Rui <rui.zhang@intel.com>
    > Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
    > Cc: Amit Kucheria <amitk@kernel.org>
    > Cc: linux-pm@vger.kernel.org
    > Signed-off-by: Kees Cook <keescook@chromium.org>

    Rui, Srinivas, any comments here?

    > ---
    > .../intel/int340x_thermal/acpi_thermal_rel.c | 5 +-
    > .../intel/int340x_thermal/acpi_thermal_rel.h | 48 ++++++++++---------
    > 2 files changed, 29 insertions(+), 24 deletions(-)
    >
    > diff --git a/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c b/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c
    > index a478cff8162a..e90690a234c4 100644
    > --- a/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c
    > +++ b/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c
    > @@ -250,8 +250,9 @@ static int fill_art(char __user *ubuf)
    > get_single_name(arts[i].source, art_user[i].source_device);
    > get_single_name(arts[i].target, art_user[i].target_device);
    > /* copy the rest int data in addition to source and target */
    > - memcpy(&art_user[i].weight, &arts[i].weight,
    > - sizeof(u64) * (ACPI_NR_ART_ELEMENTS - 2));
    > + BUILD_BUG_ON(sizeof(art_user[i].data) !=
    > + sizeof(u64) * (ACPI_NR_ART_ELEMENTS - 2));
    > + memcpy(&art_user[i].data, &arts[i].data, sizeof(art_user[i].data));
    > }
    >
    > if (copy_to_user(ubuf, art_user, art_len))
    > diff --git a/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.h b/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.h
    > index 58822575fd54..78d942477035 100644
    > --- a/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.h
    > +++ b/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.h
    > @@ -17,17 +17,19 @@
    > struct art {
    > acpi_handle source;
    > acpi_handle target;
    > - u64 weight;
    > - u64 ac0_max;
    > - u64 ac1_max;
    > - u64 ac2_max;
    > - u64 ac3_max;
    > - u64 ac4_max;
    > - u64 ac5_max;
    > - u64 ac6_max;
    > - u64 ac7_max;
    > - u64 ac8_max;
    > - u64 ac9_max;
    > + struct_group(data,
    > + u64 weight;
    > + u64 ac0_max;
    > + u64 ac1_max;
    > + u64 ac2_max;
    > + u64 ac3_max;
    > + u64 ac4_max;
    > + u64 ac5_max;
    > + u64 ac6_max;
    > + u64 ac7_max;
    > + u64 ac8_max;
    > + u64 ac9_max;
    > + );
    > } __packed;
    >
    > struct trt {
    > @@ -47,17 +49,19 @@ union art_object {
    > struct {
    > char source_device[8]; /* ACPI single name */
    > char target_device[8]; /* ACPI single name */
    > - u64 weight;
    > - u64 ac0_max_level;
    > - u64 ac1_max_level;
    > - u64 ac2_max_level;
    > - u64 ac3_max_level;
    > - u64 ac4_max_level;
    > - u64 ac5_max_level;
    > - u64 ac6_max_level;
    > - u64 ac7_max_level;
    > - u64 ac8_max_level;
    > - u64 ac9_max_level;
    > + struct_group(data,
    > + u64 weight;
    > + u64 ac0_max_level;
    > + u64 ac1_max_level;
    > + u64 ac2_max_level;
    > + u64 ac3_max_level;
    > + u64 ac4_max_level;
    > + u64 ac5_max_level;
    > + u64 ac6_max_level;
    > + u64 ac7_max_level;
    > + u64 ac8_max_level;
    > + u64 ac9_max_level;
    > + );
    > };
    > u64 __data[ACPI_NR_ART_ELEMENTS];
    > };
    > --
    > 2.30.2
    >

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