On Tue, Feb 24, 2026 at 05:43:18PM -0800, Kees Cook wrote:
> Forcing an int to be dereferenced at uint64_t for div64_u64_rem() runs
> the risk of endian confusion and stack overflowing writes. Seen while
> preparing to enable -Warray-bounds globally:
>
> In file included from ../arch/x86/include/asm/processor.h:35,
> from ../include/linux/sched.h:13,
> from ../include/linux/ratelimit.h:6,
> from ../include/linux/dev_printk.h:16,
> from
> ../drivers/gpu/drm/amd/amdgpu/../ras/ras_mgr/ras_sys.h:29,
> from ../drivers/gpu/drm/amd/amdgpu/../ras/rascore/ras.h:27,
> from
> ../drivers/gpu/drm/amd/amdgpu/../ras/rascore/ras_core.c:24:
> In function 'div64_u64_rem',
> inlined from 'ras_core_convert_timestamp_to_time' at
> ../drivers/gpu/drm/amd/amdgpu/../ras/rascore/ras_core.c:72:9:
> ../include/linux/math64.h:56:20: error: array subscript 'u64 {aka long long
> unsigned int}[0]' is partly outside array bounds of 'int[1]'
> [-Werror=array-bounds=]
> 56 | *remainder = dividend % divisor;
> | ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
> ../drivers/gpu/drm/amd/amdgpu/../ras/rascore/ras_core.c: In function
> 'ras_core_convert_timestamp_to_time':
> ../drivers/gpu/drm/amd/amdgpu/../ras/rascore/ras_core.c:70:19: note: object
> 'remaining_seconds' of size 4
> 70 | int days, remaining_seconds;
> | ^~~~~~~~~~~~~~~~~
>
> Switch remaining_seconds to uint64_t to avoid the problems.
>
> Fixes: ace232eff50e ("drm/amdgpu: Add ras module files into amdgpu")
> Signed-off-by: Kees Cook <[email protected]>
> ---
> Cc: Alex Deucher <[email protected]>
> Cc: "Christian König" <[email protected]>
> Cc: David Airlie <[email protected]>
> Cc: Simona Vetter <[email protected]>
> Cc: YiPeng Chai <[email protected]>
> Cc: Tao Zhou <[email protected]>
> Cc: Hawking Zhang <[email protected]>
> Cc: <[email protected]>
> Cc: <[email protected]>
> ---
> drivers/gpu/drm/amd/ras/rascore/ras_core.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/ras/rascore/ras_core.c
> b/drivers/gpu/drm/amd/ras/rascore/ras_core.c
> index 01122b55c98a..91e16b0b98f9 100644
> --- a/drivers/gpu/drm/amd/ras/rascore/ras_core.c
> +++ b/drivers/gpu/drm/amd/ras/rascore/ras_core.c
> @@ -63,13 +63,14 @@ int ras_core_convert_timestamp_to_time(struct
> ras_core_context *ras_core,
> {
> int days_in_month[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
> uint64_t month = 0, day = 0, hour = 0, minute = 0, second = 0;
> + uint64_t remaining_seconds;
> uint32_t year = 0;
> int seconds_per_day = 24 * 60 * 60;
> int seconds_per_hour = 60 * 60;
> int seconds_per_minute = 60;
> - int days, remaining_seconds;
> + int days;
>
> - days = div64_u64_rem(timestamp, seconds_per_day, (uint64_t
> *)&remaining_seconds);
> + days = div64_u64_rem(timestamp, seconds_per_day, &remaining_seconds);
>
> /* utc_timestamp follows the Unix epoch */
> year = 1970;
Hm, 0day noticed this creates a problem on 32-bit systems:
https://lore.kernel.org/all/[email protected]
> ld: drivers/gpu/drm/amd/ras/rascore/ras_core.o: in function
> `ras_core_convert_timestamp_to_time':
> drivers/gpu/drm/amd/amdgpu/../ras/rascore/ras_core.c:99:(.text+0x23e):
> undefined reference to `__udivmoddi4'
> ld: drivers/gpu/drm/amd/amdgpu/../ras/rascore/ras_core.c:100:(.text+0x253):
> undefined reference to `__udivdi3'
> ld: drivers/gpu/drm/amd/amdgpu/../ras/rascore/ras_core.c:101:(.text+0x265):
> undefined reference to `__umoddi3'
I will investigate and send a v2...
--
Kees Cook
