[PATCH] vhost/vsock: fix vhost vsock cid hashing inconsistent

[PATCH] vhost/vsock: fix vhost vsock cid hashing inconsistent

[Zha Bin]

The vsock core only supports 32bit CID, but the Virtio-vsock spec define
CID (dst_cid and src_cid) as u64 and the upper 32bits is reserved as
zero. This inconsistency causes one bug in vhost vsock driver. The
scenarios is:

  0. A hash table (vhost_vsock_hash) is used to map an CID to a vsock
  object. And hash_min() is used to compute the hash key. hash_min() is
  defined as:
  (sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits)).
  That means the hash algorithm has dependency on the size of macro
  argument 'val'.
  0. In function vhost_vsock_set_cid(), a 64bit CID is passed to
  hash_min() to compute the hash key when inserting a vsock object into
  the hash table.
  0. In function vhost_vsock_get(), a 32bit CID is passed to hash_min()
  to compute the hash key when looking up a vsock for an CID.

Because the different size of the CID, hash_min() returns different hash
key, thus fails to look up the vsock object for an CID.

To fix this bug, we keep CID as u64 in the IOCTLs and virtio message
headers, but explicitly convert u64 to u32 when deal with the hash table
and vsock core.

Fixes: 834e772c8db0 ("vhost/vsock: fix use-after-free in network stack callers")
Link: https://github.com/stefanha/virtio/blob/vsock/trunk/content.tex
Signed-off-by: Zha Bin <zhabin@linux.alibaba.com>
Reviewed-by: Liu Jiang <gerry@linux.alibaba.com>
---
 drivers/vhost/vsock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index bc42d38ae031..3fbc068eaa9b 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -642,7 +642,7 @@ static int vhost_vsock_set_cid(struct vhost_vsock *vsock, u64 guest_cid)
 		hash_del_rcu(&vsock->hash);
 
 	vsock->guest_cid = guest_cid;
-	hash_add_rcu(vhost_vsock_hash, &vsock->hash, guest_cid);
+	hash_add_rcu(vhost_vsock_hash, &vsock->hash, vsock->guest_cid);
 	mutex_unlock(&vhost_vsock_mutex);
 
 	return 0;
-- 
2.19.1.856.g8858448bb

Re: [PATCH] vhost/vsock: fix vhost vsock cid hashing inconsistent

[Stefan Hajnoczi]

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On Tue, Jan 08, 2019 at 04:07:03PM +0800, Zha Bin wrote:
> The vsock core only supports 32bit CID, but the Virtio-vsock spec define
> CID (dst_cid and src_cid) as u64 and the upper 32bits is reserved as
> zero. This inconsistency causes one bug in vhost vsock driver. The
> scenarios is:
> 
>   0. A hash table (vhost_vsock_hash) is used to map an CID to a vsock
>   object. And hash_min() is used to compute the hash key. hash_min() is
>   defined as:
>   (sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits)).
>   That means the hash algorithm has dependency on the size of macro
>   argument 'val'.
>   0. In function vhost_vsock_set_cid(), a 64bit CID is passed to
>   hash_min() to compute the hash key when inserting a vsock object into
>   the hash table.
>   0. In function vhost_vsock_get(), a 32bit CID is passed to hash_min()
>   to compute the hash key when looking up a vsock for an CID.
> 
> Because the different size of the CID, hash_min() returns different hash
> key, thus fails to look up the vsock object for an CID.
> 
> To fix this bug, we keep CID as u64 in the IOCTLs and virtio message
> headers, but explicitly convert u64 to u32 when deal with the hash table
> and vsock core.
> 
> Fixes: 834e772c8db0 ("vhost/vsock: fix use-after-free in network stack callers")
> Link: https://github.com/stefanha/virtio/blob/vsock/trunk/content.tex
> Signed-off-by: Zha Bin <zhabin@linux.alibaba.com>
> Reviewed-by: Liu Jiang <gerry@linux.alibaba.com>
> ---
>  drivers/vhost/vsock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Thanks for tracking this down!

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [PATCH] vhost/vsock: fix vhost vsock cid hashing inconsistent

[Christian Borntraeger]

Adding Peter,

is this the same problem that you reported me today?
Can you test Zha Bins patch?

Christian

On 08.01.2019 09:07, Zha Bin wrote:
> The vsock core only supports 32bit CID, but the Virtio-vsock spec define
> CID (dst_cid and src_cid) as u64 and the upper 32bits is reserved as
> zero. This inconsistency causes one bug in vhost vsock driver. The
> scenarios is:
> 
>   0. A hash table (vhost_vsock_hash) is used to map an CID to a vsock
>   object. And hash_min() is used to compute the hash key. hash_min() is
>   defined as:
>   (sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits)).
>   That means the hash algorithm has dependency on the size of macro
>   argument 'val'.
>   0. In function vhost_vsock_set_cid(), a 64bit CID is passed to
>   hash_min() to compute the hash key when inserting a vsock object into
>   the hash table.
>   0. In function vhost_vsock_get(), a 32bit CID is passed to hash_min()
>   to compute the hash key when looking up a vsock for an CID.
> 
> Because the different size of the CID, hash_min() returns different hash
> key, thus fails to look up the vsock object for an CID.
> 
> To fix this bug, we keep CID as u64 in the IOCTLs and virtio message
> headers, but explicitly convert u64 to u32 when deal with the hash table
> and vsock core.
> 
> Fixes: 834e772c8db0 ("vhost/vsock: fix use-after-free in network stack callers")
> Link: https://github.com/stefanha/virtio/blob/vsock/trunk/content.tex
> Signed-off-by: Zha Bin <zhabin@linux.alibaba.com>
> Reviewed-by: Liu Jiang <gerry@linux.alibaba.com>
> ---
>  drivers/vhost/vsock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index bc42d38ae031..3fbc068eaa9b 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -642,7 +642,7 @@ static int vhost_vsock_set_cid(struct vhost_vsock *vsock, u64 guest_cid)
>  		hash_del_rcu(&vsock->hash);
>  
>  	vsock->guest_cid = guest_cid;
> -	hash_add_rcu(vhost_vsock_hash, &vsock->hash, guest_cid);
> +	hash_add_rcu(vhost_vsock_hash, &vsock->hash, vsock->guest_cid);
>  	mutex_unlock(&vhost_vsock_mutex);
>  
>  	return 0;
> 

Re: [PATCH] vhost/vsock: fix vhost vsock cid hashing inconsistent

[Jason Wang]

On 2019/1/8 下午4:07, Zha Bin wrote:
> The vsock core only supports 32bit CID, but the Virtio-vsock spec define
> CID (dst_cid and src_cid) as u64 and the upper 32bits is reserved as
> zero. This inconsistency causes one bug in vhost vsock driver. The
> scenarios is:
>
>    0. A hash table (vhost_vsock_hash) is used to map an CID to a vsock
>    object. And hash_min() is used to compute the hash key. hash_min() is
>    defined as:
>    (sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits)).
>    That means the hash algorithm has dependency on the size of macro
>    argument 'val'.
>    0. In function vhost_vsock_set_cid(), a 64bit CID is passed to
>    hash_min() to compute the hash key when inserting a vsock object into
>    the hash table.
>    0. In function vhost_vsock_get(), a 32bit CID is passed to hash_min()
>    to compute the hash key when looking up a vsock for an CID.
>
> Because the different size of the CID, hash_min() returns different hash
> key, thus fails to look up the vsock object for an CID.
>
> To fix this bug, we keep CID as u64 in the IOCTLs and virtio message
> headers, but explicitly convert u64 to u32 when deal with the hash table
> and vsock core.
>
> Fixes: 834e772c8db0 ("vhost/vsock: fix use-after-free in network stack callers")
> Link: https://github.com/stefanha/virtio/blob/vsock/trunk/content.tex
> Signed-off-by: Zha Bin <zhabin@linux.alibaba.com>
> Reviewed-by: Liu Jiang <gerry@linux.alibaba.com>
> ---
>   drivers/vhost/vsock.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index bc42d38ae031..3fbc068eaa9b 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -642,7 +642,7 @@ static int vhost_vsock_set_cid(struct vhost_vsock *vsock, u64 guest_cid)
>   		hash_del_rcu(&vsock->hash);
>   
>   	vsock->guest_cid = guest_cid;
> -	hash_add_rcu(vhost_vsock_hash, &vsock->hash, guest_cid);
> +	hash_add_rcu(vhost_vsock_hash, &vsock->hash, vsock->guest_cid);
>   	mutex_unlock(&vhost_vsock_mutex);
>   
>   	return 0;


Acked-by: Jason Wang <jasowang@redhat.com>

Re: [PATCH] vhost/vsock: fix vhost vsock cid hashing inconsistent

[David Miller]

From: Zha Bin <zhabin@linux.alibaba.com>
Date: Tue,  8 Jan 2019 16:07:03 +0800

> The vsock core only supports 32bit CID, but the Virtio-vsock spec define
> CID (dst_cid and src_cid) as u64 and the upper 32bits is reserved as
> zero. This inconsistency causes one bug in vhost vsock driver. The
> scenarios is:
> 
>   0. A hash table (vhost_vsock_hash) is used to map an CID to a vsock
>   object. And hash_min() is used to compute the hash key. hash_min() is
>   defined as:
>   (sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits)).
>   That means the hash algorithm has dependency on the size of macro
>   argument 'val'.
>   0. In function vhost_vsock_set_cid(), a 64bit CID is passed to
>   hash_min() to compute the hash key when inserting a vsock object into
>   the hash table.
>   0. In function vhost_vsock_get(), a 32bit CID is passed to hash_min()
>   to compute the hash key when looking up a vsock for an CID.
> 
> Because the different size of the CID, hash_min() returns different hash
> key, thus fails to look up the vsock object for an CID.
> 
> To fix this bug, we keep CID as u64 in the IOCTLs and virtio message
> headers, but explicitly convert u64 to u32 when deal with the hash table
> and vsock core.
> 
> Fixes: 834e772c8db0 ("vhost/vsock: fix use-after-free in network stack callers")
> Link: https://github.com/stefanha/virtio/blob/vsock/trunk/content.tex
> Signed-off-by: Zha Bin <zhabin@linux.alibaba.com>
> Reviewed-by: Liu Jiang <gerry@linux.alibaba.com>

Applied, thank you.