Messages in this thread | | | Date | Mon, 13 Mar 2023 15:07:52 +0100 | From | Michal Swiatkowski <> | Subject | Re: [PATCH net v2] 9p/xen : Fix use after free bug in xen_9pfs_front_remove due to race condition |
| |
On Mon, Mar 13, 2023 at 10:01:21PM +0800, Zheng Hacker wrote: > Michal Swiatkowski <michal.swiatkowski@linux.intel.com> 于2023年3月13日周一 21:54写道: > > > > On Mon, Mar 13, 2023 at 05:00:02PM +0800, Zheng Wang wrote: > > > In xen_9pfs_front_probe, it calls xen_9pfs_front_alloc_dataring > > > to init priv->rings and bound &ring->work with p9_xen_response. > > > > > > When it calls xen_9pfs_front_event_handler to handle IRQ requests, > > > it will finally call schedule_work to start the work. > > > > > > When we call xen_9pfs_front_remove to remove the driver, there > > > may be a sequence as follows: > > > > > > Fix it by finishing the work before cleanup in xen_9pfs_front_free. > > > > > > Note that, this bug is found by static analysis, which might be > > > false positive. > > > > > > CPU0 CPU1 > > > > > > |p9_xen_response > > > xen_9pfs_front_remove| > > > xen_9pfs_front_free| > > > kfree(priv) | > > > //free priv | > > > |p9_tag_lookup > > > |//use priv->client > > > > > > Fixes: 71ebd71921e4 ("xen/9pfs: connect to the backend") > > > Signed-off-by: Zheng Wang <zyytlz.wz@163.com> > > > --- > > > v2: > > > - fix type error of ring found by kernel test robot > > > --- > > > net/9p/trans_xen.c | 5 +++++ > > > 1 file changed, 5 insertions(+) > > > > > > diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c > > > index c64050e839ac..83764431c066 100644 > > > --- a/net/9p/trans_xen.c > > > +++ b/net/9p/trans_xen.c > > > @@ -274,12 +274,17 @@ static const struct xenbus_device_id xen_9pfs_front_ids[] = { > > > static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv) > > > { > > > int i, j; > > > + struct xen_9pfs_dataring *ring = NULL; > > Move it before int i, j to have RCT. > > Sorry I didn't notice it before, move the definition to for loop.
> > > > > > write_lock(&xen_9pfs_lock); > > > list_del(&priv->list); > > > write_unlock(&xen_9pfs_lock); > > > > > > for (i = 0; i < priv->num_rings; i++) { Here: struct xen_9pfs_dataring *ring = &priv->rings[i];
> > > + /*cancel work*/ > > It isn't needed I think, the function cancel_work_sync() tells everything > > here. > > > > Get it, will remove it in the next version of patch. > > Best regards, > Zheng
| |