Re: [PATCH] firmware: arm_ffa: Fix warning caused by export_uuid()

Gavin Shan
2024-10-14T23:43:45Z

On 10/15/24 12:41 AM, Sudeep Holla wrote:
> On Mon, Oct 14, 2024 at 08:25:54PM +1000, Gavin Shan wrote:
>> On 10/14/24 8:08 PM, Sudeep Holla wrote:
>>> On Mon, Oct 14, 2024 at 10:47:24AM +1000, Gavin Shan wrote:
>>>> Run into build warning caused by export_uuid() where the UUID's
>>>> length exceeds that of ffa_value_t::a2, as the following warning
>>>> messages indicate.
>>>>
>>>> In function ‘fortify_memcpy_chk’,
>>>> inlined from ‘export_uuid’ at ./include/linux/uuid.h:88:2,
>>>> inlined from ‘ffa_msg_send_direct_req2’ at drivers/firmware/arm_ffa/driver.c:488:2:
>>>> ./include/linux/fortify-string.h:571:25: error: call to ‘__write_overflow_field’ \
>>>> declared with attribute warning: detected write beyond size of field (1st parameter); \
>>>> maybe use struct_group()? [-Werror=attribute-warning]
>>>> 571 | __write_overflow_field(p_size_field, size);
>>>> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>
>>>> Fix it by not passing a plain buffer to memcpy() to avoid the overflow
>>>> and underflow warning, similar to what have been done to copy over the
>>>> struct ffa_send_direct_data2.
>>>>
>>>
>>> Are you observing this just on the upstream or -next as well? There is a
>>> fix in the -next which I haven't sent to soc team yet, will do so soon.
>>>
>>
>> I just tried the upstream when the patch was posted. I just have a try with -next
>> and similar error exists.
>>
>> [root@nvidia-grace-hopper-01 linux-next]# git remote -v
>> origin git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git (fetch)
>> origin git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git (push)
>> [root@nvidia-grace-hopper-01 linux-next]# make W=1 drivers/firmware/arm_ffa/driver.o
>> :
>> In function ‘fortify_memcpy_chk’,
>> inlined from ‘ffa_msg_send_direct_req2’ at drivers/firmware/arm_ffa/driver.c:504:3:
>> ./include/linux/fortify-string.h:580:25: error: call to ‘__read_overflow2_field’ declared with attribute warning: \
>> detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror=attribute-warning]
>> 580 | __read_overflow2_field(q_size_field, size);
>> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> cc1: all warnings being treated as errors
>>
>>
>> Part of the changes included this patch is still needed by -next. Could you please
>> squeeze the changes to that one to be pulled?
>
> Sure I can do that. Can you share the build command(specifically if any
> extra warning are enabled) and the toolchain used ? I am unable to reproduce
> it with clang 20.0.0, not sure if it my toolchain or build command/flags that
> differs here.
>

Thanks, Sudeep. I think what matters is 'W=1', which is translated to '-DKBUILD_EXTRA_WARN1'.
With KBUILD_EXTRA_WARN1 declared in linux-next, the warning is raised by __read_overflow2_field().

static int ffa_msg_send_direct_req2(u16 src_id, u16 dst_id, const uuid_t *uuid,
struct ffa_send_direct_data2 *data)
{
:
if (ret.a0 == FFA_MSG_SEND_DIRECT_RESP2) {
memcpy(data, &ret.a4, sizeof(*data));
return 0;
}

return -EINVAL;
}

memcpy
__fortify_memcpy_chk
fortify_memcpy_chk

__FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
const size_t p_size,
const size_t q_size,
const size_t p_size_field,
const size_t q_size_field,
const u8 func)
{
if (__builtin_constant_p(size)) {
:
/*
* Warn for source field over-read when building with W=1
* or when an over-write happened, so both can be fixed at
* the same time.
*/
if ((IS_ENABLED(KBUILD_EXTRA_WARN1) || <<< true: KBUILD_EXTRA_WARN1 is declared
__compiletime_lessthan(p_size_field, size)) && <<< false: sizeof(*data) == sizeof(*data)
__compiletime_lessthan(q_size_field, size)) <<< true: sizeof(ret.a4) < sizeof(*data)
__read_overflow2_field(q_size_field, size); <<< where the warning is reported
}
:
}

[root@nvidia-grace-hopper-01 linux-next]# cat /etc/redhat-release
Red Hat Enterprise Linux release 9.6 Beta (Plow)
[root@nvidia-grace-hopper-01 linux-next]# gcc --version
gcc (GCC) 11.5.0 20240719 (Red Hat 11.5.0-2)
[root@nvidia-grace-hopper-01 linux-next]# clang --version
clang version 18.1.8 (Red Hat, Inc. 18.1.8-3.el9)
Target: aarch64-redhat-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Configuration file: /etc/clang/aarch64-redhat-linux-gnu-clang.cfg

[root@nvidia-grace-hopper-01 linux-next]# make V=1 W=1 drivers/firmware/arm_ffa/driver.o
:
# CC [M] drivers/firmware/arm_ffa/driver.o
gcc -Wp,-MMD,drivers/firmware/arm_ffa/.driver.o.d -nostdinc -I./arch/arm64/include -I./arch/arm64/include/generated -I./include -I./arch/arm64/include/uapi -I./arch/arm64/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -mlittle-endian -DCC_USING_PATCHABLE_FUNCTION_ENTRY -DKASAN_SHADOW_SCALE_SHIFT= -fmacro-prefix-map=./= -Werror -Wundef -DKBUILD_EXTRA_WARN1 -std=gnu11 -fshort-wchar -funsigned-char -fno-common -fno-PIE -fno-strict-aliasing -mgeneral-regs-only -DCONFIG_CC_HAS_K_CONSTRAINT=1 -Wno-psabi -mabi=lp64 -fno-asynchronous-unwind-tables -fno-unwind-tables -mbranch-protection=none -Wa,-march=armv8.5-a -DARM64_ASM_ARCH='"armv8.5-a"' -DKASAN_SHADOW_SCALE_SHIFT= -fno-delete-null-pointer-checks -O2 -fno-allow-store-data-races -fstack-protector-strong -fno-omit-frame-pointer -fno-optimize-sibling-calls -fno-stack-clash-protection -fpatchable-function-entry=4,2 -fno-inline-functions-called-once -falign-functions=8 -fno-strict-overflow -fno-stack-check -fconserve-stack -Wall -Wundef -Werror=implicit-function-declaration -Werror=implicit-int -Werror=return-type -Werror=strict-prototypes -Wno-format-security -Wno-trigraphs -Wno-frame-address -Wno-address-of-packed-member -Wmissing-declarations -Wmissing-prototypes -Wframe-larger-than=2048 -Wno-main -Wvla -Wno-pointer-sign -Wcast-function-type -Wno-stringop-overflow -Wno-array-bounds -Wno-alloc-size-larger-than -Wimplicit-fallthrough=5 -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -Wenum-conversion -Wextra -Wunused -Wmissing-format-attribute -Wmissing-include-dirs -Wunused-const-variable -Wno-missing-field-initializers -Wno-type-limits -Wno-shift-negative-value -Wno-maybe-uninitialized -Wno-sign-compare -Wno-unused-parameter -g -mstack-protector-guard=sysreg -mstack-protector-guard-reg=sp_el0 -mstack-protector-guard-offset=1992 -DMODULE -DKBUILD_BASENAME='"driver"' -DKBUILD_MODNAME='"ffa_module"' -D__KBUILD_MODNAME=kmod_ffa_module -c -o drivers/firmware/arm_ffa/driver.o drivers/firmware/arm_ffa/driver.c
In file included from ./include/linux/string.h:390,
from ./include/linux/bitmap.h:13,
from ./include/linux/cpumask.h:12,
from ./arch/arm64/include/asm/cpufeature.h:27,
from ./arch/arm64/include/asm/ptrace.h:11,
from ./arch/arm64/include/asm/irqflags.h:9,
from ./include/linux/irqflags.h:18,
from ./include/linux/spinlock.h:59,
from ./include/linux/mmzone.h:8,
from ./include/linux/gfp.h:7,
from ./include/linux/slab.h:16,
from ./include/linux/resource_ext.h:11,
from ./include/linux/acpi.h:13,
from drivers/firmware/arm_ffa/driver.c:25:
In function ‘fortify_memcpy_chk’,
inlined from ‘ffa_msg_send_direct_req2’ at drivers/firmware/arm_ffa/driver.c:504:3:
./include/linux/fortify-string.h:580:25: error: call to ‘__read_overflow2_field’ declared with attribute warning: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror=attribute-warning]
580 | __read_overflow2_field(q_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
[root@nvidia-grace-hopper-01 linux-next]# echo $?
2

[root@nvidia-grace-hopper-01 linux-next]# make V=1 drivers/firmware/arm_ffa/driver.o
:
# CC [M] drivers/firmware/arm_ffa/driver.o
gcc -Wp,-MMD,drivers/firmware/arm_ffa/.driver.o.d -nostdinc -I./arch/arm64/include -I./arch/arm64/include/generated -I./include -I./arch/arm64/include/uapi -I./arch/arm64/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -mlittle-endian -DCC_USING_PATCHABLE_FUNCTION_ENTRY -DKASAN_SHADOW_SCALE_SHIFT= -fmacro-prefix-map=./= -Werror -std=gnu11 -fshort-wchar -funsigned-char -fno-common -fno-PIE -fno-strict-aliasing -mgeneral-regs-only -DCONFIG_CC_HAS_K_CONSTRAINT=1 -Wno-psabi -mabi=lp64 -fno-asynchronous-unwind-tables -fno-unwind-tables -mbranch-protection=none -Wa,-march=armv8.5-a -DARM64_ASM_ARCH='"armv8.5-a"' -DKASAN_SHADOW_SCALE_SHIFT= -fno-delete-null-pointer-checks -O2 -fno-allow-store-data-races -fstack-protector-strong -fno-omit-frame-pointer -fno-optimize-sibling-calls -fno-stack-clash-protection -fpatchable-function-entry=4,2 -fno-inline-functions-called-once -falign-functions=8 -fno-strict-overflow -fno-stack-check -fconserve-stack -Wall -Wundef -Werror=implicit-function-declaration -Werror=implicit-int -Werror=return-type -Werror=strict-prototypes -Wno-format-security -Wno-trigraphs -Wno-frame-address -Wno-address-of-packed-member -Wmissing-declarations -Wmissing-prototypes -Wframe-larger-than=2048 -Wno-main -Wvla -Wno-pointer-sign -Wcast-function-type -Wno-stringop-overflow -Wno-array-bounds -Wno-alloc-size-larger-than -Wimplicit-fallthrough=5 -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -Wenum-conversion -Wextra -Wunused -Wno-unused-but-set-variable -Wno-unused-const-variable -Wno-packed-not-aligned -Wno-format-overflow -Wno-format-truncation -Wno-stringop-truncation -Wno-override-init -Wno-missing-field-initializers -Wno-type-limits -Wno-shift-negative-value -Wno-maybe-uninitialized -Wno-sign-compare -Wno-unused-parameter -g -mstack-protector-guard=sysreg -mstack-protector-guard-reg=sp_el0 -mstack-protector-guard-offset=1992 -DMODULE -DKBUILD_BASENAME='"driver"' -DKBUILD_MODNAME='"ffa_module"' -D__KBUILD_MODNAME=kmod_ffa_module -c -o drivers/firmware/arm_ffa/driver.o drivers/firmware/arm_ffa/driver.c
[root@nvidia-grace-hopper-01 linux-next]# echo $?
0

Thanks,
Gavin