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

---

dri-devel mailing list dri-devel@lists.freedesktop.org https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.free...

Am 22.06.20 um 15:45 schrieb Nirmoy Das:

Function prepare_igt_frag() and get_insert_time() were casting signed value to unsigned value before returning error. So error check in igt_frag() would not work with unsigned return value from get_insert_time() compared against negative value.

Addresses-Coverity: ("Unsigned compared against 0, no effect") Signed-off-by: Nirmoy Das nirmoy.das@amd.com Reported-by: Colin Ian King colin.king@canonical.com

Reviewed-by: Christian König christian.koenig@amd.com

---

drivers/gpu/drm/selftests/test-drm_mm.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/selftests/test-drm_mm.c b/drivers/gpu/drm/selftests/test-drm_mm.c index 3846b0f5bae3..3306d8bd0544 100644 --- a/drivers/gpu/drm/selftests/test-drm_mm.c +++ b/drivers/gpu/drm/selftests/test-drm_mm.c @@ -1041,13 +1041,12 @@ static int prepare_igt_frag(struct drm_mm *mm, { unsigned int size = 4096; unsigned int i;

• u64 ret = -EINVAL;

  for (i = 0; i < num_insert; i++) { if (!expect_insert(mm, &nodes[i], size, 0, i, mode) != 0) { pr_err("%s insert failed\n", mode->name);

• 	goto out;
  

• 	return -EINVAL;
  

  } }

@@ -1057,8 +1056,7 @@ static int prepare_igt_frag(struct drm_mm *mm, drm_mm_remove_node(&nodes[i]); }

-out:

• return ret;

• return 0;

  }

@@ -1070,21 +1068,16 @@ static u64 get_insert_time(struct drm_mm *mm, unsigned int size = 8192; ktime_t start; unsigned int i;

• u64 ret = -EINVAL;

  start = ktime_get(); for (i = 0; i < num_insert; i++) { if (!expect_insert(mm, &nodes[i], size, 0, i, mode) != 0) { pr_err("%s insert failed\n", mode->name);

• 	goto out;
  

• 	return 0;
  

  } }

• ret = ktime_to_ns(ktime_sub(ktime_get(), start));

-out:

• return ret;

• return ktime_to_ns(ktime_sub(ktime_get(), start)); }

  static int igt_frag(void *ignored)

@@ -1119,17 +1112,17 @@ static int igt_frag(void *ignored) continue;

ret = prepare_igt_frag(&mm, nodes, insert_size, mode);

• if (!ret)
  

• if (ret)
  goto err;
  
  

  insert_time1 = get_insert_time(&mm, insert_size, nodes + insert_size, mode);

• if (insert_time1 < 0)
  

• if (insert_time1 == 0)
  goto err;
  
  

  insert_time2 = get_insert_time(&mm, (insert_size * 2), nodes + insert_size * 2, mode);

• if (insert_time2 < 0)
  

• if (insert_time2 == 0)
  goto err;
  
  

  pr_info("%s fragmented insert of %u and %u insertions took %llu and %llu nsecs\n",

-- 2.27.0