[PATCH] powerpc/kernel: Initialize load_tm on task creation

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[PATCH] powerpc/kernel: Initialize load_tm on task creation

Breno Leitao-2
Currently tsk->thread.load_tm is not initialized in the task creation
and can contain garbage on a new task.

This is an undesired behaviour, since it affects the timing to enable
and disable the transactional memory laziness (disabling and enabling
the MSR TM bit, which affects TM reclaim and recheckpoint in the
scheduling process).

CC: Anton Blanchard <[hidden email]>
Fixes: 5d176f751ee3c6eededd984ad409bff201f436a7
Signed-off-by: Breno Leitao <[hidden email]>
---
 arch/powerpc/kernel/process.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index a9435397eab8..2ad725ef4368 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1687,6 +1687,7 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
  current->thread.tm_tfhar = 0;
  current->thread.tm_texasr = 0;
  current->thread.tm_tfiar = 0;
+ current->thread.load_tm = 0;
 #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
 }
 EXPORT_SYMBOL(start_thread);
--
2.11.0

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Re: [PATCH] powerpc/kernel: Initialize load_tm on task creation

Daniel Axtens
Hi Breno,

Looks good to me.

> Currently tsk->thread.load_tm is not initialized in the task creation
> and can contain garbage on a new task.
>
> This is an undesired behaviour, since it affects the timing to enable
> and disable the transactional memory laziness (disabling and enabling
> the MSR TM bit, which affects TM reclaim and recheckpoint in the
> scheduling process).

Is there any chance this uninitialised memory will leak something
interesting/sensitive? (Therefore, should this go to stable?)

Regards,
Daniel


> CC: Anton Blanchard <[hidden email]>
> Fixes: 5d176f751ee3c6eededd984ad409bff201f436a7
> Signed-off-by: Breno Leitao <[hidden email]>
> ---
>  arch/powerpc/kernel/process.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index a9435397eab8..2ad725ef4368 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1687,6 +1687,7 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
>   current->thread.tm_tfhar = 0;
>   current->thread.tm_texasr = 0;
>   current->thread.tm_tfiar = 0;
> + current->thread.load_tm = 0;
>  #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
>  }
>  EXPORT_SYMBOL(start_thread);
> --
> 2.11.0
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Re: [PATCH] powerpc/kernel: Initialize load_tm on task creation

Michael Ellerman-2
Daniel Axtens <[hidden email]> writes:

> Hi Breno,
>
> Looks good to me.
>
>> Currently tsk->thread.load_tm is not initialized in the task creation
>> and can contain garbage on a new task.
>>
>> This is an undesired behaviour, since it affects the timing to enable
>> and disable the transactional memory laziness (disabling and enabling
>> the MSR TM bit, which affects TM reclaim and recheckpoint in the
>> scheduling process).
>
> Is there any chance this uninitialised memory will leak something
> interesting/sensitive? (Therefore, should this go to stable?)

I'll send it to stable anyway for the original bug it fixes.

cheers
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Re: powerpc/kernel: Initialize load_tm on task creation

Michael Ellerman-3
In reply to this post by Breno Leitao-2
On Mon, 2017-06-05 at 14:40:59 UTC, Breno Leitao wrote:

> Currently tsk->thread.load_tm is not initialized in the task creation
> and can contain garbage on a new task.
>
> This is an undesired behaviour, since it affects the timing to enable
> and disable the transactional memory laziness (disabling and enabling
> the MSR TM bit, which affects TM reclaim and recheckpoint in the
> scheduling process).
>
> CC: Anton Blanchard <[hidden email]>
> Fixes: 5d176f751ee3c6eededd984ad409bff201f436a7
> Signed-off-by: Breno Leitao <[hidden email]>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/7f22ced4377628074e2ac25f41a88f

cheers