Re: [PATCH] kernel/smp.c: fix a panic as cp->info is used wrongly and a list corruption

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On Wed, May 13, 2015 at 05:03:04PM +0800, Pan Xinhui wrote:
> this patch reverts commit 3440a1ca99707f093e9568ba9762764d3162dd8f which causes the regression.
> 
> base knowledge: kernel call cp->func using cp->info as its argument. like cp->func(cp->info);
> 
> current code is totally wrong, as 1) &softirq is at stack. 2) cp->info don't point to struct call_single_data.
> So in remote_softirq_receive,
> 1) If the caller had left __try_remote_softirq, dereferencing cp->info could not fetch the correct value.
> 2) And we can't get struct call_single_data *cp anymore.
> 
> The list corruption is below.
> __local_trigger will add cp->list into softirq_work_list. But no one will delete cp->list on behalf of us.
> if we can succeed to raise_softirq_irqoff, we must delete it from softirq_work_list. because we has lost control of pointer cp.
> cp is passed in and may be freed later in other places.
> 
> Cc: <stable@xxxxxxxxxxxxxxx> # 3.10
> Signed-off-by: xinhuix.pan <xinhuix.pan@xxxxxxxxx>
> ---
>  include/linux/smp.h |  1 +
>  kernel/softirq.c    | 10 +++++++---
>  2 files changed, 8 insertions(+), 3 deletions(-)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read Documentation/stable_kernel_rules.txt
for how to do this properly.

</formletter>
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