linux-kernel - RE: [PATCH hyperv-next v4 13/16] Drivers: hv: Free msginfo when the buffer fails to decrypt

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Message-ID:
 <SN6PR02MB4157BBB94F6D2D7592B17C14D45CA@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Tue, 22 Jul 2025 17:45:05 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Roman Kisel <romank@...ux.microsoft.com>, "alok.a.tiwari@...cle.com"
	<alok.a.tiwari@...cle.com>, "arnd@...db.de" <arnd@...db.de>, "bp@...en8.de"
	<bp@...en8.de>, "corbet@....net" <corbet@....net>,
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	"decui@...rosoft.com" <decui@...rosoft.com>, "haiyangz@...rosoft.com"
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	<mingo@...hat.com>, "rdunlap@...radead.org" <rdunlap@...radead.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>, "Tianyu.Lan@...rosoft.com"
	<Tianyu.Lan@...rosoft.com>, "wei.liu@...nel.org" <wei.liu@...nel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
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	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
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CC: "apais@...rosoft.com" <apais@...rosoft.com>, "benhill@...rosoft.com"
	<benhill@...rosoft.com>, "bperkins@...rosoft.com" <bperkins@...rosoft.com>,
	"sunilmut@...rosoft.com" <sunilmut@...rosoft.com>
Subject: RE: [PATCH hyperv-next v4 13/16] Drivers: hv: Free msginfo when the
 buffer fails to decrypt

From: Roman Kisel <romank@...ux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
> 
> The early failure path in __vmbus_establish_gpadl() doesn't deallocate
> msginfo if the buffer fails to decrypt.
> 
> Fix the leak by breaking out the cleanup code into a separate function
> and calling it where required.
> 
> Fixes: d4dccf353db80 ("Drivers: hv: vmbus: Mark vmbus ring buffer visible to host in Isolation VM")
> Reported-by: Michael Kelly <mkhlinux@...look.com>

s/Kelly/Kelley/

> Closes: https://lore.kernel.org/linux-hyperv/SN6PR02MB41573796F9787F67E0E97049D472A@SN6PR02MB4157.namprd02.prod.outlook.com/ 
> Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
> ---
>  drivers/hv/channel.c | 32 ++++++++++++++++++++++----------
>  1 file changed, 22 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 051eeba800f2..0eb300b940db 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -409,6 +409,25 @@ static int create_gpadl_header(enum hv_gpadl_type type, void *kbuffer,
>  	return 0;
>  }
> 
> +static void vmbus_free_channel_msginfo(struct vmbus_channel_msginfo *msginfo)
> +{
> +	unsigned long flags;
> +	struct vmbus_channel_msginfo *submsginfo, *tmp;
> +
> +	if (!msginfo)
> +		return;
> +
> +	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
> +	list_del(&msginfo->msglistentry);
> +	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
> +	list_for_each_entry_safe(submsginfo, tmp, &msginfo->submsglist,
> +				 msglistentry) {
> +		kfree(submsginfo);
> +	}
> +
> +	kfree(msginfo);
> +}
> +
>  /*
>   * __vmbus_establish_gpadl - Establish a GPADL for a buffer or ringbuffer
>   *
> @@ -428,7 +447,7 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
>  	struct vmbus_channel_gpadl_header *gpadlmsg;
>  	struct vmbus_channel_gpadl_body *gpadl_body;
>  	struct vmbus_channel_msginfo *msginfo = NULL;
> -	struct vmbus_channel_msginfo *submsginfo, *tmp;
> +	struct vmbus_channel_msginfo *submsginfo;
>  	struct list_head *curr;
>  	u32 next_gpadl_handle;
>  	unsigned long flags;
> @@ -458,6 +477,7 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
>  			dev_warn(&channel->device_obj->device,
>  				"Failed to set host visibility for new GPADL %d.\n",
>  				ret);
> +			vmbus_free_channel_msginfo(msginfo);

I don't think this works. At this point, msginfo has not been added to the global
vmbus_connection.chn_msg_list.  vmbus_free_channel_msginfo() will try to
remove it from that list using list_del(), and will fault on a NULL pointer.

>  			return ret;
>  		}
>  	}
> @@ -531,15 +551,7 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> 
> 
>  cleanup:
> -	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
> -	list_del(&msginfo->msglistentry);
> -	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
> -	list_for_each_entry_safe(submsginfo, tmp, &msginfo->submsglist,
> -				 msglistentry) {
> -		kfree(submsginfo);
> -	}
> -
> -	kfree(msginfo);
> +	vmbus_free_channel_msginfo(msginfo);
> 
>  	if (ret) {
>  		/*
> --
> 2.43.0