[PATCH] time/timgr: Fix wrong reference when level 0 group allocation failed

[PATCH] time/timgr: Fix wrong reference when level 0 group allocation failed

[Levi Yun]

When tmigr_setup_groups() failed level 0 group allocation,
next do while loop refers wrong local stack array location.

Changing group init do while loop with while loop to fix this problem.

Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
---
 kernel/time/timer_migration.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index ccba875d2234..84413114db5c 100644
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -1596,7 +1596,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 
 	} while (i < tmigr_hierarchy_levels);
 
-	do {
+	while (i > 0) {
 		group = stack[--i];
 
 		if (err < 0) {
@@ -1645,7 +1645,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 				tmigr_connect_child_parent(child, group);
 			}
 		}
-	} while (i > 0);
+	}
 
 	kfree(stack);
 
-- 
2.41.0

Re: [PATCH] time/timgr: Fix wrong reference when level 0 group allocation failed

[Yun Levi]

Gentle ping

On Wed, May 1, 2024 at 8:51 PM Levi Yun <ppbuk5246@gmail.com> wrote:
>
> When tmigr_setup_groups() failed level 0 group allocation,
> next do while loop refers wrong local stack array location.
>
> Changing group init do while loop with while loop to fix this problem.
>
> Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
> ---
>  kernel/time/timer_migration.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
> index ccba875d2234..84413114db5c 100644
> --- a/kernel/time/timer_migration.c
> +++ b/kernel/time/timer_migration.c
> @@ -1596,7 +1596,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
>
>         } while (i < tmigr_hierarchy_levels);
>
> -       do {
> +       while (i > 0) {
>                 group = stack[--i];
>
>                 if (err < 0) {
> @@ -1645,7 +1645,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
>                                 tmigr_connect_child_parent(child, group);
>                         }
>                 }
> -       } while (i > 0);
> +       }
>
>         kfree(stack);
>
> --
> 2.41.0
>

Re: [PATCH] time/timgr: Fix wrong reference when level 0 group allocation failed

[Markus Elfring]

> Changing group init do while loop with while loop to fix this problem.

* Please convert such a change description to an improved imperative wording.

* Would you like to add the tag “Fixes” accordingly?


Regards,
Markus

[PATCH RESEND] time/timgr: Fix wrong reference when level 0 group allocation failed

[Levi Yun]

When tmigr_setup_groups() failed level 0 group allocation,
wrong reference happens on local stack array while intializing timer hierarchy.

To prevent this, Check loop condition first before intializing timer hierarchy.


Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
---
 kernel/time/timer_migration.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index ccba875d2234..84413114db5c 100644
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -1596,7 +1596,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)

 	} while (i < tmigr_hierarchy_levels);

-	do {
+	while (i > 0) {
 		group = stack[--i];

 		if (err < 0) {
@@ -1645,7 +1645,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 				tmigr_connect_child_parent(child, group);
 			}
 		}
-	} while (i > 0);
+	}

 	kfree(stack);

--
2.41.0

Re: [PATCH RESEND] time/timgr: Fix wrong reference when level 0 group allocation failed

[Markus Elfring]

…
> To prevent this, Check loop condition first before intializing timer hierarchy.
…
> Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
…

Does this change approach represent a subsequent patch version instead of a “RESEND”?

How do you think about to add a patch changelog accordingly?

Regards,
Markus

[PATCH v2] time/timgr: Fix wrong reference when level 0 group allocation failed

[Levi Yun]

When tmigr_setup_groups() failed level 0 group allocation,
wrong reference happens on local stack array while intializing timer hierarchy.

To prevent this, Check loop condition first before intializing timer hierarchy.

Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
---

v2:
	- Modify commit message.

 kernel/time/timer_migration.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index ccba875d2234..84413114db5c 100644
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -1596,7 +1596,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)

 	} while (i < tmigr_hierarchy_levels);

-	do {
+	while (i > 0) {
 		group = stack[--i];

 		if (err < 0) {
@@ -1645,7 +1645,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 				tmigr_connect_child_parent(child, group);
 			}
 		}
-	} while (i > 0);
+	}

 	kfree(stack);

--
2.41.0

Re: [PATCH RESEND] time/timgr: Fix wrong reference when level 0 group allocation failed

[Yun Levi]

Hi Markus :)


> Does this change approach represent a subsequent patch version instead of a “RESEND”?
>
> How do you think about to add a patch changelog accordingly?
>
Thanks I'll do

Thanks.

Re: [v2] time/timgr: Fix wrong reference when level 0 group allocation failed

[Markus Elfring]

…
> To prevent this, Check loop condition first before intializing timer hierarchy.

I suggest to avoid another typo (also in the email address for Frederic Weisbecker).

Regards,
Markus

[PATCH v3] time/timgr: Fix wrong reference when level 0 group allocation failed

[Levi Yun]

When tmigr_setup_groups() failed level 0 group allocation,
wrong reference happens on local stack array while intializing timer hierarchy.

To prevent this, Check loop condition first before initializing timer hierarchy.

Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
---
v3:
    - Fix typo.

v2:
	- Modify commit message.

 kernel/time/timer_migration.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index ccba875d2234..84413114db5c 100644
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -1596,7 +1596,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)

 	} while (i < tmigr_hierarchy_levels);

-	do {
+	while (i > 0) {
 		group = stack[--i];

 		if (err < 0) {
@@ -1645,7 +1645,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 				tmigr_connect_child_parent(child, group);
 			}
 		}
-	} while (i > 0);
+	}

 	kfree(stack);

--
2.41.0

Re: [PATCH v3] time/timgr: Fix wrong reference when level 0 group allocation failed

[Frederic Weisbecker]

Le Mon, May 06, 2024 at 05:10:59AM +0100, Levi Yun a écrit :
> When tmigr_setup_groups() failed level 0 group allocation,
> wrong reference happens on local stack array while intializing timer hierarchy.
> 
> To prevent this, Check loop condition first before initializing timer hierarchy.
> 
> Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
> Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
> ---
> v3:
>     - Fix typo.
> 
> v2:
> 	- Modify commit message.
> 
>  kernel/time/timer_migration.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
> index ccba875d2234..84413114db5c 100644
> --- a/kernel/time/timer_migration.c
> +++ b/kernel/time/timer_migration.c
> @@ -1596,7 +1596,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
> 
>  	} while (i < tmigr_hierarchy_levels);
> 
> -	do {
> +	while (i > 0) {
>  		group = stack[--i];
> 
>  		if (err < 0) {
> @@ -1645,7 +1645,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
>  				tmigr_connect_child_parent(child, group);
>  			}
>  		}
> -	} while (i > 0);
> +	}

Looks good to me. But let's wait for Anna-Maria's second look. The group setup
is not my favourite area...

Thanks.

> 
>  	kfree(stack);
> 
> --
> 2.41.0

Re: [PATCH v3] time/timgr: Fix wrong reference when level 0 group allocation failed

[Anna-Maria Behnsen]

Frederic Weisbecker <frederic@kernel.org> writes:

> Le Mon, May 06, 2024 at 05:10:59AM +0100, Levi Yun a écrit :
>> When tmigr_setup_groups() failed level 0 group allocation,
>> wrong reference happens on local stack array while intializing timer hierarchy.
>> 
>> To prevent this, Check loop condition first before initializing timer hierarchy.
>> 
>> Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
>> Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
>> ---
>> v3:
>>     - Fix typo.
>> 
>> v2:
>> 	- Modify commit message.
>> 
>>  kernel/time/timer_migration.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
>> index ccba875d2234..84413114db5c 100644
>> --- a/kernel/time/timer_migration.c
>> +++ b/kernel/time/timer_migration.c
>> @@ -1596,7 +1596,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
>> 
>>  	} while (i < tmigr_hierarchy_levels);
>> 
>> -	do {
>> +	while (i > 0) {
>>  		group = stack[--i];
>> 
>>  		if (err < 0) {
>> @@ -1645,7 +1645,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
>>  				tmigr_connect_child_parent(child, group);
>>  			}
>>  		}
>> -	} while (i > 0);
>> +	}
>
> Looks good to me. But let's wait for Anna-Maria's second look. The group setup
> is not my favourite area...
>

Thanks for the fix!

Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>

Re: [v3] time/timgr: Fix wrong reference when level 0 group allocation failed

[Markus Elfring]

…
>>> To prevent this, Check loop condition first before initializing timer hierarchy.
…
>>> ---
>>> v3:
>>>     - Fix typo.
>>>
>>> v2:
>>> 	- Modify commit message.
>>>
>>>  kernel/time/timer_migration.c | 4 ++--
…
> Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>

Do you find any remaining wording concerns less relevant fur such a changelog?

Regards,
Markus

[tip: timers/urgent] timers/migration: Prevent out of bounds access on failure

[tip-bot2 for Levi Yun]

The following commit has been merged into the timers/urgent branch of tip:

Commit-ID:     d7ad05c86e2191bd66e5b62fca8da53c4a53484f
Gitweb:        https://git.kernel.org/tip/d7ad05c86e2191bd66e5b62fca8da53c4a53484f
Author:        Levi Yun <ppbuk5246@gmail.com>
AuthorDate:    Mon, 06 May 2024 05:10:59 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Wed, 08 May 2024 11:19:43 +02:00

timers/migration: Prevent out of bounds access on failure

When tmigr_setup_groups() fails the level 0 group allocation, then the
cleanup derefences index -1 of the local stack array.

Prevent this by checking the loop condition first.

Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Link: https://lore.kernel.org/r/20240506041059.86877-1-ppbuk5246@gmail.com
---
 kernel/time/timer_migration.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index ccba875..8441311 100644
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -1596,7 +1596,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 
 	} while (i < tmigr_hierarchy_levels);
 
-	do {
+	while (i > 0) {
 		group = stack[--i];
 
 		if (err < 0) {
@@ -1645,7 +1645,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 				tmigr_connect_child_parent(child, group);
 			}
 		}
-	} while (i > 0);
+	}
 
 	kfree(stack);
 

Re: [tip: timers/urgent] timers/migration: Prevent out of bounds access on failure

[Andy Shevchenko]

On Wed, May 08, 2024 at 09:45:41AM -0000, tip-bot2 for Levi Yun wrote:
> The following commit has been merged into the timers/urgent branch of tip:

(Yes, I noted above)

...

> -	do {
> +	while (i > 0) {
>  		group = stack[--i];

Looking at this and most used patterns for cleanup loops, I would amend
this to

	while (i--) {
		group = stack[i];

which seems to me an equivalent.

>  		if (err < 0) {
> @@ -1645,7 +1645,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
>  				tmigr_connect_child_parent(child, group);
>  			}
>  		}
> -	} while (i > 0);
> +	}

-- 
With Best Regards,
Andy Shevchenko