Re: [PATCH] 9p/xen: fix release of IRQ

[Dominique Martinet <asmadeus@xxxxxxxxxxxxx>]

Alexander Merritt wrote on Thu, Nov 21, 2024 at 10:51:00PM +0000:
> From: Alex Zenla <alex@xxxxxxxxx>
> 
> Kernel logs indicate an IRQ was double-freed.

Nit: if you still have the log it'd be great to include it in the commit
message, rather than paragraphing it.

The rationale is that someone with the same problem will likely just
search for the error as is first, and having it in the commit log will
be an easy hit.

(This alone wouldn't need a resend, I can add it if you just reply to
the mail with it; it's also fine if you no longer have the log, that'll
be a remark for the next patch)


> 
> Pass correct device ID during IRQ release.
> 
> Fixes: 71ebd71921e45 ("xen/9pfs: connect to the backend")
> Signed-off-by: Alex Zenla <alex@xxxxxxxxx>
> Signed-off-by: Alexander Merritt <alexander@xxxxxxxxx>
> Signed-off-by: Ariadne Conill <ariadne@ariadne.space>



> ---
>  net/9p/trans_xen.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
> index dfdbe1ca5338..198d46d79d84 100644
> --- a/net/9p/trans_xen.c
> +++ b/net/9p/trans_xen.c
> @@ -286,7 +286,8 @@ static void xen_9pfs_front_free(struct 
> xen_9pfs_front_priv *priv)
>               if (!priv->rings[i].intf)
>                       break;
>               if (priv->rings[i].irq > 0)
> -                     unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
> +                     unbind_from_irqhandler(priv->rings[i].irq, ring);
> +             priv->rings[i].evtchn = priv->rings[i].irq = 0;

(style) I don't recall seeing much `a = b = 0` in the kernel, and
looking at it checkpatch seems to complain:
CHECK: multiple assignments should be avoided
#114: FILE: net/9p/trans_xen.c:290:
+               priv->rings[i].evtchn = priv->rings[i].irq = 0;

Please run checkpatch on the patches you send (b4 can do it for you if
you want to start using it)


code-wise,
I also don't see where unbinf_from_irqhandler would free the evtchn, so
is it leaking here, or is it implicit from something else?
We only free it explicitly on error binding the irq.



Thanks,
-- 
Dominique Martinet | Asmadeus