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xen-9pfs: disconnect if buffers are misconfigured
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Implement xen_9pfs_disconnect by unbinding the event channels. On
xen_9pfs_free, call disconnect if any event channels haven't been
disconnected.

If the frontend misconfigured the buffers set the backend to "Closing"
and disconnect it. Misconfigurations include requesting a read of more
bytes than available on the ring buffer, or claiming to be writing more
data than available on the ring buffer.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
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@sstabellini @gkurz
sstabellini authored and gkurz committed Jun 29, 2017
1 parent 8d37de4 commit e08d1e1
Showing 1 changed file with 64 additions and 21 deletions.
85 changes: 64 additions & 21 deletions hw/9pfs/xen-9p-backend.c
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Expand Up @@ -54,6 +54,8 @@ typedef struct Xen9pfsDev {
Xen9pfsRing *rings;
} Xen9pfsDev;

static void xen_9pfs_disconnect(struct XenDevice *xendev);

static void xen_9pfs_in_sg(Xen9pfsRing *ring,
struct iovec *in_sg,
int *num,
Expand Down Expand Up @@ -125,10 +127,19 @@ static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
struct iovec in_sg[2];
int num;
ssize_t ret;

xen_9pfs_in_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
in_sg, &num, pdu->idx, ROUND_UP(offset + 128, 512));
return v9fs_iov_vmarshal(in_sg, num, offset, 0, fmt, ap);

ret = v9fs_iov_vmarshal(in_sg, num, offset, 0, fmt, ap);
if (ret < 0) {
xen_pv_printf(&xen_9pfs->xendev, 0,
"Failed to encode VirtFS request type %d\n", pdu->id + 1);
xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
xen_9pfs_disconnect(&xen_9pfs->xendev);
}
return ret;
}

static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
Expand All @@ -139,10 +150,19 @@ static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
struct iovec out_sg[2];
int num;
ssize_t ret;

xen_9pfs_out_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
out_sg, &num, pdu->idx);
return v9fs_iov_vunmarshal(out_sg, num, offset, 0, fmt, ap);

ret = v9fs_iov_vunmarshal(out_sg, num, offset, 0, fmt, ap);
if (ret < 0) {
xen_pv_printf(&xen_9pfs->xendev, 0,
"Failed to decode VirtFS request type %d\n", pdu->id);
xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
xen_9pfs_disconnect(&xen_9pfs->xendev);
}
return ret;
}

static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
Expand Down Expand Up @@ -170,11 +190,22 @@ static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
int num;
size_t buf_size;

g_free(ring->sg);

ring->sg = g_malloc0(sizeof(*ring->sg) * 2);
xen_9pfs_in_sg(ring, ring->sg, &num, pdu->idx, size);

buf_size = iov_size(ring->sg, num);
if (buf_size < size) {
xen_pv_printf(&xen_9pfs->xendev, 0, "Xen 9pfs request type %d"
"needs %zu bytes, buffer has %zu\n", pdu->id, size,
buf_size);
xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
xen_9pfs_disconnect(&xen_9pfs->xendev);
}

*piov = ring->sg;
*pniov = num;
}
Expand Down Expand Up @@ -218,7 +249,7 @@ static int xen_9pfs_init(struct XenDevice *xendev)
static int xen_9pfs_receive(Xen9pfsRing *ring)
{
P9MsgHeader h;
RING_IDX cons, prod, masked_prod, masked_cons;
RING_IDX cons, prod, masked_prod, masked_cons, queued;
V9fsPDU *pdu;

if (ring->inprogress) {
Expand All @@ -229,8 +260,8 @@ static int xen_9pfs_receive(Xen9pfsRing *ring)
prod = ring->intf->out_prod;
xen_rmb();

if (xen_9pfs_queued(prod, cons, XEN_FLEX_RING_SIZE(ring->ring_order)) <
sizeof(h)) {
queued = xen_9pfs_queued(prod, cons, XEN_FLEX_RING_SIZE(ring->ring_order));
if (queued < sizeof(h)) {
return 0;
}
ring->inprogress = true;
Expand All @@ -241,6 +272,9 @@ static int xen_9pfs_receive(Xen9pfsRing *ring)
xen_9pfs_read_packet((uint8_t *) &h, ring->ring.out, sizeof(h),
masked_prod, &masked_cons,
XEN_FLEX_RING_SIZE(ring->ring_order));
if (queued < le32_to_cpu(h.size_le)) {
return 0;
}

/* cannot fail, because we only handle one request per ring at a time */
pdu = pdu_alloc(&ring->priv->state);
Expand Down Expand Up @@ -269,15 +303,30 @@ static void xen_9pfs_evtchn_event(void *opaque)
qemu_bh_schedule(ring->bh);
}

static int xen_9pfs_free(struct XenDevice *xendev)
static void xen_9pfs_disconnect(struct XenDevice *xendev)
{
Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
int i;

for (i = 0; i < xen_9pdev->num_rings; i++) {
if (xen_9pdev->rings[i].evtchndev != NULL) {
qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
NULL, NULL, NULL);
xenevtchn_unbind(xen_9pdev->rings[i].evtchndev,
xen_9pdev->rings[i].local_port);
xen_9pdev->rings[i].evtchndev = NULL;
}
}
}

static int xen_9pfs_free(struct XenDevice *xendev)
{
Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
int i;

g_free(xen_9pdev->id);
g_free(xen_9pdev->tag);
g_free(xen_9pdev->path);
g_free(xen_9pdev->security_model);
if (xen_9pdev->rings[0].evtchndev != NULL) {
xen_9pfs_disconnect(xendev);
}

for (i = 0; i < xen_9pdev->num_rings; i++) {
if (xen_9pdev->rings[i].data != NULL) {
Expand All @@ -290,16 +339,15 @@ static int xen_9pfs_free(struct XenDevice *xendev)
xen_9pdev->rings[i].intf,
1);
}
if (xen_9pdev->rings[i].evtchndev > 0) {
qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
NULL, NULL, NULL);
xenevtchn_unbind(xen_9pdev->rings[i].evtchndev,
xen_9pdev->rings[i].local_port);
}
if (xen_9pdev->rings[i].bh != NULL) {
qemu_bh_delete(xen_9pdev->rings[i].bh);
}
}

g_free(xen_9pdev->id);
g_free(xen_9pdev->tag);
g_free(xen_9pdev->path);
g_free(xen_9pdev->security_model);
g_free(xen_9pdev->rings);
return 0;
}
Expand Down Expand Up @@ -423,11 +471,6 @@ static void xen_9pfs_alloc(struct XenDevice *xendev)
xenstore_write_be_int(xendev, "max-ring-page-order", MAX_RING_ORDER);
}

static void xen_9pfs_disconnect(struct XenDevice *xendev)
{
/* Dynamic hotplug of PV filesystems at runtime is not supported. */
}

struct XenDevOps xen_9pfs_ops = {
.size = sizeof(Xen9pfsDev),
.flags = DEVOPS_FLAG_NEED_GNTDEV,
Expand Down

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