[PATCH i-g-t] lib/igt_list: igt_list_empty() Detect uninitialized list

[PATCH i-g-t] lib/igt_list: igt_list_empty() Detect uninitialized list

[Peter Senna Tschudin]

Add a check to igt_list_empty() to return true if the list head pointer
or its next/prev pointers are NULL, preventing segfaults when operating
on uninitialized or potentially broken lists.

Signed-off-by: Peter Senna Tschudin <peter.senna@linux.intel.com>
---
 lib/igt_list.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/igt_list.c b/lib/igt_list.c
index 37ae139c4..f77aef7dd 100644
--- a/lib/igt_list.c
+++ b/lib/igt_list.c
@@ -79,5 +79,9 @@ int igt_list_length(const struct igt_list_head *head)
 
 bool igt_list_empty(const struct igt_list_head *head)
 {
+	/* Detect uninitialized / potentially broken list */
+	if (!head || !head->next || !head->prev)
+		return true;
+
 	return head->next == head;
 }
-- 
2.43.0

✓ Xe.CI.BAT: success for lib/igt_list: igt_list_empty() Detect uninitialized list

[Patchwork]

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== Series Details ==

Series: lib/igt_list: igt_list_empty() Detect uninitialized list
URL   : https://patchwork.freedesktop.org/series/154855/
State : success

== Summary ==

CI Bug Log - changes from XEIGT_8548_BAT -> XEIGTPW_13797_BAT
====================================================

Summary
-------

  **WARNING**

  Minor unknown changes coming with XEIGTPW_13797_BAT need to be verified
  manually.
  
  If you think the reported changes have nothing to do with the changes
  introduced in XEIGTPW_13797_BAT, please notify your bug team (I915-ci-infra@lists.freedesktop.org) to allow them
  to document this new failure mode, which will reduce false positives in CI.

  

Participating hosts (11 -> 11)
------------------------------

  No changes in participating hosts

Possible new issues
-------------------

  Here are the unknown changes that may have been introduced in XEIGTPW_13797_BAT:

### IGT changes ###

#### Warnings ####

  * igt@xe_module_load@load:
    - bat-bmg-1:          [ABORT][1] ([Intel XE#6201]) -> [ABORT][2]
   [1]: https://intel-gfx-ci.01.org/tree/intel-xe/IGT_8548/bat-bmg-1/igt@xe_module_load@load.html
   [2]: https://intel-gfx-ci.01.org/tree/intel-xe/IGTPW_13797/bat-bmg-1/igt@xe_module_load@load.html

  
Known issues
------------

  Here are the changes found in XEIGTPW_13797_BAT that come from known issues:

### IGT changes ###

  {name}: This element is suppressed. This means it is ignored when computing
          the status of the difference (SUCCESS, WARNING, or FAILURE).

  [Intel XE#6201]: https://gitlab.freedesktop.org/drm/xe/kernel/issues/6201


Build changes
-------------

  * IGT: IGT_8548 -> IGTPW_13797

  IGTPW_13797: 13797
  IGT_8548: 8548
  xe-3813-3ff214d6c6a86025aa3feadcb5bba4abfc2dd8f1: 3ff214d6c6a86025aa3feadcb5bba4abfc2dd8f1

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/intel-xe/IGTPW_13797/index.html

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✗ i915.CI.BAT: failure for lib/igt_list: igt_list_empty() Detect uninitialized list

[Patchwork]

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== Series Details ==

Series: lib/igt_list: igt_list_empty() Detect uninitialized list
URL   : https://patchwork.freedesktop.org/series/154855/
State : failure

== Summary ==

CI Bug Log - changes from IGT_8548 -> IGTPW_13797
====================================================

Summary
-------

  **FAILURE**

  Serious unknown changes coming with IGTPW_13797 absolutely need to be
  verified manually.
  
  If you think the reported changes have nothing to do with the changes
  introduced in IGTPW_13797, please notify your bug team (I915-ci-infra@lists.freedesktop.org) to allow them
  to document this new failure mode, which will reduce false positives in CI.

  External URL: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/index.html

Participating hosts (39 -> 38)
------------------------------

  Missing    (1): bat-adls-6 

Possible new issues
-------------------

  Here are the unknown changes that may have been introduced in IGTPW_13797:

### IGT changes ###

#### Possible regressions ####

  * igt@core_auth@basic-auth:
    - fi-glk-j4005:       NOTRUN -> [INCOMPLETE][1]
   [1]: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/fi-glk-j4005/igt@core_auth@basic-auth.html

  * igt@i915_selftest@live@requests:
    - bat-atsm-1:         [PASS][2] -> [DMESG-WARN][3]
   [2]: https://intel-gfx-ci.01.org/tree/drm-tip/IGT_8548/bat-atsm-1/igt@i915_selftest@live@requests.html
   [3]: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/bat-atsm-1/igt@i915_selftest@live@requests.html

  * igt@kms_force_connector_basic@force-edid:
    - bat-kbl-2:          NOTRUN -> [ABORT][4]
   [4]: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/bat-kbl-2/igt@kms_force_connector_basic@force-edid.html

  * igt@runner@aborted:
    - fi-glk-j4005:       NOTRUN -> [FAIL][5]
   [5]: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/fi-glk-j4005/igt@runner@aborted.html

  
Known issues
------------

  Here are the changes found in IGTPW_13797 that come from known issues:

### IGT changes ###

#### Issues hit ####

  * igt@kms_force_connector_basic@force-connector-state:
    - fi-kbl-8809g:       [PASS][6] -> [ABORT][7] ([i915#15020])
   [6]: https://intel-gfx-ci.01.org/tree/drm-tip/IGT_8548/fi-kbl-8809g/igt@kms_force_connector_basic@force-connector-state.html
   [7]: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/fi-kbl-8809g/igt@kms_force_connector_basic@force-connector-state.html

  
#### Possible fixes ####

  * igt@i915_module_load@load:
    - fi-glk-j4005:       [ABORT][8] ([i915#15020]) -> [PASS][9]
   [8]: https://intel-gfx-ci.01.org/tree/drm-tip/IGT_8548/fi-glk-j4005/igt@i915_module_load@load.html
   [9]: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/fi-glk-j4005/igt@i915_module_load@load.html

  * igt@kms_force_connector_basic@force-connector-state:
    - bat-kbl-2:          [ABORT][10] ([i915#15020]) -> [PASS][11]
   [10]: https://intel-gfx-ci.01.org/tree/drm-tip/IGT_8548/bat-kbl-2/igt@kms_force_connector_basic@force-connector-state.html
   [11]: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/bat-kbl-2/igt@kms_force_connector_basic@force-connector-state.html

  
#### Warnings ####

  * igt@i915_module_load@load:
    - fi-elk-e7500:       [ABORT][12] -> [ABORT][13] ([i915#15020])
   [12]: https://intel-gfx-ci.01.org/tree/drm-tip/IGT_8548/fi-elk-e7500/igt@i915_module_load@load.html
   [13]: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/fi-elk-e7500/igt@i915_module_load@load.html

  * igt@i915_selftest@live:
    - bat-atsm-1:         [DMESG-FAIL][14] ([i915#12061] / [i915#14204]) -> [DMESG-FAIL][15] ([i915#12061] / [i915#13929])
   [14]: https://intel-gfx-ci.01.org/tree/drm-tip/IGT_8548/bat-atsm-1/igt@i915_selftest@live.html
   [15]: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/bat-atsm-1/igt@i915_selftest@live.html

  * igt@i915_selftest@live@mman:
    - bat-atsm-1:         [DMESG-FAIL][16] ([i915#14204]) -> [DMESG-FAIL][17] ([i915#13929])
   [16]: https://intel-gfx-ci.01.org/tree/drm-tip/IGT_8548/bat-atsm-1/igt@i915_selftest@live@mman.html
   [17]: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/bat-atsm-1/igt@i915_selftest@live@mman.html

  
  [i915#12061]: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12061
  [i915#13929]: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13929
  [i915#14204]: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14204
  [i915#15020]: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15020


Build changes
-------------

  * CI: CI-20190529 -> None
  * IGT: IGT_8548 -> IGTPW_13797

  CI-20190529: 20190529
  CI_DRM_17254: 3ff214d6c6a86025aa3feadcb5bba4abfc2dd8f1 @ git://anongit.freedesktop.org/gfx-ci/linux
  IGTPW_13797: 13797
  IGT_8548: 8548

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_13797/index.html

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✓ Xe.CI.Full: success for lib/igt_list: igt_list_empty() Detect uninitialized list

[Patchwork]

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== Series Details ==

Series: lib/igt_list: igt_list_empty() Detect uninitialized list
URL   : https://patchwork.freedesktop.org/series/154855/
State : success

== Summary ==

CI Bug Log - changes from XEIGT_8548_FULL -> XEIGTPW_13797_FULL
====================================================

Summary
-------

  **SUCCESS**

  No regressions found.

  

Participating hosts (4 -> 3)
------------------------------

  Missing    (1): shard-adlp 


Changes
-------

  No changes found


Build changes
-------------

  * IGT: IGT_8548 -> IGTPW_13797

  IGTPW_13797: 13797
  IGT_8548: 8548
  xe-3813-3ff214d6c6a86025aa3feadcb5bba4abfc2dd8f1: 3ff214d6c6a86025aa3feadcb5bba4abfc2dd8f1

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/intel-xe/IGTPW_13797/index.html

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Re: [PATCH i-g-t] lib/igt_list: igt_list_empty() Detect uninitialized list

[Manszewski, Christoph]

Hi Peter,

On 22.09.2025 18:23, Peter Senna Tschudin wrote:
> Add a check to igt_list_empty() to return true if the list head pointer
> or its next/prev pointers are NULL, preventing segfaults when operating
> on uninitialized or potentially broken lists.
> 
> Signed-off-by: Peter Senna Tschudin <peter.senna@linux.intel.com>
> ---
>   lib/igt_list.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/lib/igt_list.c b/lib/igt_list.c
> index 37ae139c4..f77aef7dd 100644
> --- a/lib/igt_list.c
> +++ b/lib/igt_list.c
> @@ -79,5 +79,9 @@ int igt_list_length(const struct igt_list_head *head)
>   
>   bool igt_list_empty(const struct igt_list_head *head)
>   {
> +	/* Detect uninitialized / potentially broken list */
> +	if (!head || !head->next || !head->prev)
> +		return true;
> +

Without this change:
1. Passing an uninitialized list is a bug
2. The function doesn't check any condition and returns 'normally' 
regardless

With this change:
1. Passing an uninitialized list is a bug (still)
2. The function *may* detect an uninitialized list which is a bug but 
returns 'normally' regardless

If we are adding a check that catches some invalid/buggy condition the 
reasonable thing to do would be to assert/abort.

Regards,
Christoph


>   	return head->next == head;
>   }

Re: [PATCH i-g-t] lib/igt_list: igt_list_empty() Detect uninitialized list

[Peter Senna Tschudin]

Hi Christoph,

On 9/23/2025 10:14 AM, Manszewski, Christoph wrote:
> Hi Peter,
> 
> On 22.09.2025 18:23, Peter Senna Tschudin wrote:
>> Add a check to igt_list_empty() to return true if the list head pointer
>> or its next/prev pointers are NULL, preventing segfaults when operating
>> on uninitialized or potentially broken lists.
>>
>> Signed-off-by: Peter Senna Tschudin <peter.senna@linux.intel.com>
>> ---
>>   lib/igt_list.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/lib/igt_list.c b/lib/igt_list.c
>> index 37ae139c4..f77aef7dd 100644
>> --- a/lib/igt_list.c
>> +++ b/lib/igt_list.c
>> @@ -79,5 +79,9 @@ int igt_list_length(const struct igt_list_head *head)
>>     bool igt_list_empty(const struct igt_list_head *head)
>>   {
>> +    /* Detect uninitialized / potentially broken list */
>> +    if (!head || !head->next || !head->prev)
>> +        return true;
>> +
> 
> Without this change:
> 1. Passing an uninitialized list is a bug
> 2. The function doesn't check any condition and returns 'normally'
> regardless
> 
> With this change:
> 1. Passing an uninitialized list is a bug (still)
> 2. The function *may* detect an uninitialized list which is a bug but
> returns 'normally' regardless
> 
> If we are adding a check that catches some invalid/buggy condition the
> reasonable thing to do would be to assert/abort.

I agree with you. I would say that even more concerning is to distance
our implementation from the kernel implementation. I suggest we nack
this change. If you are ok with it

Nacked-by: Peter Senna Tschudin <peter.senna@linux.intel.com>

> 
> Regards,
> Christoph
> 
> 
>>       return head->next == head;
>>   }
> 

Re: [PATCH i-g-t] lib/igt_list: igt_list_empty() Detect uninitialized list

[Manszewski, Christoph]

Hi Peter,

On 23.09.2025 11:20, Peter Senna Tschudin wrote:
> Hi Christoph,
> 
> On 9/23/2025 10:14 AM, Manszewski, Christoph wrote:
>> Hi Peter,
>>
>> On 22.09.2025 18:23, Peter Senna Tschudin wrote:
>>> Add a check to igt_list_empty() to return true if the list head pointer
>>> or its next/prev pointers are NULL, preventing segfaults when operating
>>> on uninitialized or potentially broken lists.
>>>
>>> Signed-off-by: Peter Senna Tschudin <peter.senna@linux.intel.com>
>>> ---
>>>    lib/igt_list.c | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>>
>>> diff --git a/lib/igt_list.c b/lib/igt_list.c
>>> index 37ae139c4..f77aef7dd 100644
>>> --- a/lib/igt_list.c
>>> +++ b/lib/igt_list.c
>>> @@ -79,5 +79,9 @@ int igt_list_length(const struct igt_list_head *head)
>>>      bool igt_list_empty(const struct igt_list_head *head)
>>>    {
>>> +    /* Detect uninitialized / potentially broken list */
>>> +    if (!head || !head->next || !head->prev)
>>> +        return true;
>>> +
>>
>> Without this change:
>> 1. Passing an uninitialized list is a bug
>> 2. The function doesn't check any condition and returns 'normally'
>> regardless
>>
>> With this change:
>> 1. Passing an uninitialized list is a bug (still)
>> 2. The function *may* detect an uninitialized list which is a bug but
>> returns 'normally' regardless
>>
>> If we are adding a check that catches some invalid/buggy condition the
>> reasonable thing to do would be to assert/abort.
> 
> I agree with you. I would say that even more concerning is to distance
> our implementation from the kernel implementation. I suggest we nack
> this change. If you are ok with it

Well either way is fine with by me. I just wanted to make a point that 
when we add a check that catches a bug it makes sense to alarm the 
developer right away.

Regards,
Christoph

> 
> Nacked-by: Peter Senna Tschudin <peter.senna@linux.intel.com>
> 
>>
>> Regards,
>> Christoph
>>
>>
>>>        return head->next == head;
>>>    }
>>
>