Re: [PATCH][next] drm/mm/selftests: fix unsigned comparison with less than zero
From: Nirmoy
Date: Sun Jun 21 2020 - 17:37:25 EST
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@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
---
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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