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SubjectRe: [PATCH][next] drm/mm/selftests: fix unsigned comparison with less than zero
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On 6/18/20 12:39 PM, Dan Carpenter wrote:
> On Wed, Jun 17, 2020 at 04:59:59PM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> Function get_insert_time can return error values that are cast
>> to a u64. The checks of insert_time1 and insert_time2 check for
>> the errors but because they are u64 variables the check for less
>> than zero can never be true. Fix this by casting the value to s64
>> to allow of the negative error check to succeed.
>>
>> Addresses-Coverity: ("Unsigned compared against 0, no effect")
>> Fixes: 6e60d5ded06b ("drm/mm: add ig_frag selftest")
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>> drivers/gpu/drm/selftests/test-drm_mm.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/selftests/test-drm_mm.c b/drivers/gpu/drm/selftests/test-drm_mm.c
>> index 3846b0f5bae3..671a152a6df2 100644
>> --- a/drivers/gpu/drm/selftests/test-drm_mm.c
>> +++ b/drivers/gpu/drm/selftests/test-drm_mm.c
>> @@ -1124,12 +1124,12 @@ static int igt_frag(void *ignored)
>>
>> insert_time1 = get_insert_time(&mm, insert_size,
>> nodes + insert_size, mode);
>> - if (insert_time1 < 0)
>> + if ((s64)insert_time1 < 0)
>> goto err;
> The error codes in this function seem pretty messed up.
>
> Speaking of error codes, what the heck is going on with
> prepare_igt_frag().


This is on me. I will send a patch to correct this mistake.


Thanks,

Nirmoy


>
> 1037 static int prepare_igt_frag(struct drm_mm *mm,
> 1038 struct drm_mm_node *nodes,
> 1039 unsigned int num_insert,
> 1040 const struct insert_mode *mode)
> 1041 {
> 1042 unsigned int size = 4096;
> 1043 unsigned int i;
> 1044 u64 ret = -EINVAL;
> ^^^^^^^^^^^^^^^^^^
> Why is it u64?
>
> 1045
> 1046 for (i = 0; i < num_insert; i++) {
> 1047 if (!expect_insert(mm, &nodes[i], size, 0, i,
> 1048 mode) != 0) {
> 1049 pr_err("%s insert failed\n", mode->name);
> 1050 goto out;
> ^^^^^^^^
> One of the common bugs with do nothing gotos is that we forget to set
> the error code. If we did a direct "return -EINVAL;" here, then there
> would be no ambiguity.
>
> 1051 }
> 1052 }
> 1053
> 1054 /* introduce fragmentation by freeing every other node */
> 1055 for (i = 0; i < num_insert; i++) {
> 1056 if (i % 2 == 0)
> 1057 drm_mm_remove_node(&nodes[i]);
> 1058 }
> 1059
> 1060 out:
> 1061 return ret;
> 1062
> 1063 }
>
> regards,
> dan carpenter
>
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