[PATCH v2] drm/amdgpu: fix overflowed array index read warning

[Christian König]

Am 25.04.24 um 15:28 schrieb Alex Deucher:
> On Thu, Apr 25, 2024 at 3:22 AM Tim Huang <tim.huang at amd.com> wrote:
>> From: Tim Huang <Tim.Huang at amd.com>
>>
>> Clear warning that cast operation might have overflowed.
>>
>> v2: keep reverse xmas tree order to declare "int r;" (Christian)
>>
>> Signed-off-by: Tim Huang <Tim.Huang at amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
>> index 06f0a6534a94..8cf60acb2970 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
>> @@ -473,8 +473,8 @@ static ssize_t amdgpu_debugfs_ring_read(struct file *f, char __user *buf,
>>                                          size_t size, loff_t *pos)
>>   {
>>          struct amdgpu_ring *ring = file_inode(f)->i_private;
>> -       int r, i;
>>          uint32_t value, result, early[3];
>> +       int r;
>>
>>          if (*pos & 3 || size & 3)
>>                  return -EINVAL;
>> @@ -485,7 +485,7 @@ static ssize_t amdgpu_debugfs_ring_read(struct file *f, char __user *buf,
>>                  early[0] = amdgpu_ring_get_rptr(ring) & ring->buf_mask;
>>                  early[1] = amdgpu_ring_get_wptr(ring) & ring->buf_mask;
>>                  early[2] = ring->wptr & ring->buf_mask;
>> -               for (i = *pos / 4; i < 3 && size; i++) {
>> +               for (loff_t i = *pos / 4; i < 3 && size; i++) {
> Some older compilers complain about declarations mixed with code like
> this.  Not sure how big a deal that would be.

Good point, we would like to be able to backport this.

Somebody from Alivins team needs to comment, but IIRC we agreed that 
this would be legal and we take care of it by using appropriate compiler 
flags on older kernels.

Christian.

>
> Alex
>
>>                          r = put_user(early[i], (uint32_t *)buf);
>>                          if (r)
>>                                  return r;
>> --
>> 2.39.2
>>