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

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Message-ID: <a6570b47-217c-4e92-a64c-16fc34494e3e@suse.com>
Date: Fri, 22 Nov 2024 14:54:06 +0100
From: Jürgen Groß <jgross@...e.com>
To: Dominique Martinet <asmadeus@...ewreck.org>,
 Alexander Merritt <alexander@...ra.dev>
Cc: v9fs@...ts.linux.dev, linux-kernel@...r.kernel.org,
 xen-devel@...ts.xenproject.org, Eric Van Hensbergen <ericvh@...nel.org>,
 Latchesar Ionkov <lucho@...kov.net>,
 Christian Schoenebeck <linux_oss@...debyte.com>,
 Stefano Stabellini <sstabellini@...nel.org>, Alex Zenla <alex@...ra.dev>,
 Ariadne Conill <ariadne@...adne.space>
Subject: Re: [PATCH] 9p/xen: fix release of IRQ

On 22.11.24 00:44, Dominique Martinet wrote:
> Alexander Merritt wrote on Thu, Nov 21, 2024 at 10:51:00PM +0000:
>> From: Alex Zenla <alex@...ra.dev>
>>
>> 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@...ra.dev>
>> Signed-off-by: Alexander Merritt <alexander@...ra.dev>
>> Signed-off-by: Ariadne Conill <ariadne@...adne.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.

unbind_from_irqhandler()
   unbind_from_irq()
     __unbind_from_irq()
       close_evtchn()


Juergen

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