Re: [syzbot] [kernel?] general protection fault in vhost_task_start

[Mike Christie <michael.christie@oracle.com>]

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@oracle.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;