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authorAl Viro <viro@zeniv.linux.org.uk>2022-05-16 16:42:13 +0800
committerAl Viro <viro@zeniv.linux.org.uk>2022-05-18 12:33:51 -0400
commitfb4554c2232e44d595920f4d5c66cf8f7d13f9bc (patch)
treeb11f7865439a1f0325d8c7ff14d976fba82d3213 /drivers
parenta91714312eb16f9ecd1f7f8b3efe1380075f28d4 (diff)
Fix double fget() in vhost_net_set_backend()
Descriptor table is a shared resource; two fget() on the same descriptor may return different struct file references. get_tap_ptr_ring() is called after we'd found (and pinned) the socket we'll be using and it tries to find the private tun/tap data structures associated with it. Redoing the lookup by the same file descriptor we'd used to get the socket is racy - we need to same struct file. Thanks to Jason for spotting a braino in the original variant of patch - I'd missed the use of fd == -1 for disabling backend, and in that case we can end up with sock == NULL and sock != oldsock. Cc: stable@kernel.org Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/vhost/net.c15
1 files changed, 7 insertions, 8 deletions
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 792ab5f23647..297b5db47454 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1450,13 +1450,9 @@ err:
return ERR_PTR(r);
}
-static struct ptr_ring *get_tap_ptr_ring(int fd)
+static struct ptr_ring *get_tap_ptr_ring(struct file *file)
{
struct ptr_ring *ring;
- struct file *file = fget(fd);
-
- if (!file)
- return NULL;
ring = tun_get_tx_ring(file);
if (!IS_ERR(ring))
goto out;
@@ -1465,7 +1461,6 @@ static struct ptr_ring *get_tap_ptr_ring(int fd)
goto out;
ring = NULL;
out:
- fput(file);
return ring;
}
@@ -1552,8 +1547,12 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
r = vhost_net_enable_vq(n, vq);
if (r)
goto err_used;
- if (index == VHOST_NET_VQ_RX)
- nvq->rx_ring = get_tap_ptr_ring(fd);
+ if (index == VHOST_NET_VQ_RX) {
+ if (sock)
+ nvq->rx_ring = get_tap_ptr_ring(sock->file);
+ else
+ nvq->rx_ring = NULL;
+ }
oldubufs = nvq->ubufs;
nvq->ubufs = ubufs;