# Re: \[PATCH v2\] hvc/xen: lock console list traversal

- From: Juergen Gross \<jgross@suse.com\>
- Date: 2023-01-10 08:07:36 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2023/01/2060838
- Thread: https://ratatoskr.run/xen-devel/2022/11/2025740/t.md

```text
On 30.11.22 17:36, Roger Pau Monne wrote:
> The currently lockless access to the xen console list in
> vtermno_to_xencons() is incorrect, as additions and removals from the
> list can happen anytime, and as such the traversal of the list to get
> the private console data for a given termno needs to happen with the
> lock held.  Note users that modify the list already do so with the
> lock taken.
>
> Adjust current lock takers to use the _irq{save,restore} helpers,
> since the context in which vtermno_to_xencons() is called can have
> interrupts disabled.  Use the _irq{save,restore} set of helpers to
> switch the current callers to disable interrupts in the locked region.
> I haven't checked if existing users could instead use the _irq
> variant, as I think it's safer to use _irq{save,restore} upfront.
>
> While there switch from using list_for_each_entry_safe to
> list_for_each_entry: the current entry cursor won't be removed as
> part of the code in the loop body, so using the _safe variant is
> pointless.
>
> Fixes: 02e19f9c7cac ('hvc_xen: implement multiconsole support')
> Signed-off-by: Roger Pau Monné <redacted>

Pushed to xen/tip.git for-linus-6.2


Juergen

```

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