diff options
| author | Olaf Hering | 2011-08-25 18:30:11 +0200 |
|---|---|---|
| committer | Konrad Rzeszutek Wilk | 2011-09-01 11:48:29 -0400 |
| commit | c4c303c7c5679b4b368e12f41124aee29c325b76 (patch) | |
| tree | 53f98a9bc550edca6f3c6619ec3d363186e0521d /drivers/xen | |
| parent | 02f8c6aee8df3cdc935e9bdd4f2d020306035dbe (diff) | |
xen/pv-on-hvm kexec: prevent crash in xenwatch_thread() when stale watch events arrive
During repeated kexec boots xenwatch_thread() can crash because
xenbus_watch->callback is cleared by xenbus_watch_path() if a node/token
combo for a new watch happens to match an already registered watch from
an old kernel. In this case xs_watch returns -EEXISTS, then
register_xenbus_watch() does not remove the to-be-registered watch from
the list of active watches but returns the -EEXISTS to the caller
anyway.
Because the watch is still active in xenstored it will cause an event
which will arrive in the new kernel. process_msg() will find the
encapsulated struct xenbus_watch in its list of registered watches and
puts the "empty" watch handle in the queue for xenwatch_thread().
xenwatch_thread() then calls ->callback which was cleared earlier by
xenbus_watch_path().
To prevent that crash in a guest running on an old xen toolstack remove
the special -EEXIST handling.
v2:
- remove the EEXIST handing in register_xenbus_watch() instead of
checking for ->callback in process_msg()
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Diffstat (limited to 'drivers/xen')
| -rw-r--r-- | drivers/xen/xenbus/xenbus_xs.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c index 5534690075af..46347a49c5b8 100644 --- a/drivers/xen/xenbus/xenbus_xs.c +++ b/drivers/xen/xenbus/xenbus_xs.c @@ -638,8 +638,7 @@ int register_xenbus_watch(struct xenbus_watch *watch) err = xs_watch(watch->node, token); - /* Ignore errors due to multiple registration. */ - if ((err != 0) && (err != -EEXIST)) { + if (err) { spin_lock(&watches_lock); list_del(&watch->list); spin_unlock(&watches_lock); |