netdev - Re: [syzbot] [kernel?] general protection fault in vhost_task

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Date:   Tue, 21 Mar 2023 13:54:55 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Mike Christie <michael.christie@...cle.com>
Cc:     syzbot <syzbot+6b27b2d2aba1c80cc13b@...kaller.appspotmail.com>,
        brauner@...nel.org, jasowang@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com,
        virtualization@...ts.linux-foundation.org
Subject: Re: [syzbot] [kernel?] general protection fault in vhost_task_start

On Tue, Mar 21, 2023 at 12:46:04PM -0500, Mike Christie wrote:
> On 3/21/23 12:03 PM, syzbot wrote:
> > RIP: 0010:vhost_task_start+0x22/0x40 kernel/vhost_task.c:115
> > Code: 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 53 48 89 fb e8 c3 67 2c 00 48 8d 7b 70 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 0a 48 8b 7b 70 5b e9 fe bd 02 00 e8 79 ec 7e 00 eb
> > RSP: 0018:ffffc90003a9fc38 EFLAGS: 00010207
> > RAX: dffffc0000000000 RBX: fffffffffffffff4 RCX: 0000000000000000
> > RDX: 000000000000000c RSI: ffffffff81564c8d RDI: 0000000000000064
> > RBP: ffff88802b21dd40 R08: 0000000000000100 R09: ffffffff8c917cf3
> > R10: 00000000fffffff4 R11: 0000000000000000 R12: fffffffffffffff4
> > R13: ffff888075d000b0 R14: ffff888075d00000 R15: ffff888075d00008
> > FS:  0000555556247300(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007ffe3d8e5ff8 CR3: 00000000215d4000 CR4: 00000000003506f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >  <TASK>
> >  vhost_worker_create drivers/vhost/vhost.c:580 [inline]
> 
> The return value from vhost_task_create is incorrect if the kzalloc fails.
> 
> Christian, here is a fix for what's in your tree. Do you want me to submit
> a follow up patch like this or a replacement patch for:
> 
> commit 77feab3c4156 ("vhost_task: Allow vhost layer to use copy_process")
> 
> with the fix rolled into it?
> 



> 
> >From 0677ad6d77722f301ca35e8e0f8fd0cbd5ed8484 Mon Sep 17 00:00:00 2001
> From: Mike Christie <michael.christie@...cle.com>
> Date: Tue, 21 Mar 2023 12:39:39 -0500
> Subject: [PATCH] vhost_task: Fix vhost_task_create return value
> 
> vhost_task_create is supposed to return the vhost_task or NULL on
> failure. This fixes it to return the correct value when the allocation
> of the struct fails.
> ---
>  kernel/vhost_task.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c
> index 4b8aff160640..b7cbd66f889e 100644
> --- a/kernel/vhost_task.c
> +++ b/kernel/vhost_task.c
> @@ -88,7 +88,7 @@ struct vhost_task *vhost_task_create(int (*fn)(void *), void *arg,
>  
>  	vtsk = kzalloc(sizeof(*vtsk), GFP_KERNEL);
>  	if (!vtsk)
> -		return ERR_PTR(-ENOMEM);
> +		return NULL;
>  	init_completion(&vtsk->exited);
>  	vtsk->data = arg;
>  	vtsk->fn = fn;
>