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author | Al Viro <viro@zeniv.linux.org.uk> | 2022-05-16 11:42:13 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-05-25 10:17:55 +0300 |
commit | ec0d801d1a44d9259377142c6218885ecd685e41 (patch) | |
tree | 04d13871e9020a0b1ae2422380a91c58323942e1 /drivers/vhost | |
parent | b42e5e3a84ddbcbb104d7c69003aac806cdcdf26 (diff) | |
download | linux-ec0d801d1a44d9259377142c6218885ecd685e41.tar.xz |
Fix double fget() in vhost_net_set_backend()
commit fb4554c2232e44d595920f4d5c66cf8f7d13f9bc upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/vhost')
-rw-r--r-- | drivers/vhost/net.c | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index e303f6f073d2..5beb20768b20 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; |