From: Olaf Hering Date: Thu, 25 Aug 2011 16:30:11 +0000 (+0200) Subject: xen/pv-on-hvm kexec: prevent crash in xenwatch_thread() when stale watch events arrive X-Git-Tag: v3.2-rc1~192^2~7 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c4c303c7c5679b4b368e12f41124aee29c325b76;p=pandora-kernel.git 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 Signed-off-by: Olaf Hering --- Reading git-diff-tree failed