** Branch linked: lp:~ubuntu-branches/ubuntu/utopic/linux-flo/utopic- proposed
-- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1323526 Title: apparmor spam log with warnings on Preempt kernels Status in “linux” package in Ubuntu: Fix Released Status in “linux” source package in Trusty: Confirmed Status in “linux” source package in Utopic: Fix Released Bug description: The apparmor/dbus support needs to allocate buffers in atomic context (i.e: holding a spinlock) since that is not possible, it declares a static per cpu array of buffers and has accessor macros to get and put buffers. Since the buffer array is a per cpu variable, it can only be concurrently accessed by the same cpu and this can only happen if the kernel is preempted. So the get_buffers() macro disables preemption with preempt_disable() so the buffer can be accessed safely. Grabbing a spinlock also makes the kernel to disable preemption so a raw __get_buffers() function can be used in this case that does not call preempt_disable(). The raw __get_buffers() function was called from file_path_perm() since a spinlock was held by the calling revalidate_tty() function. But this is not the only place where file_path_perm() is called, it is also called by match_file() which is not in atomic context and thus doesn't disable preemption before so the __get_buffers() macro was complaining with a WARN_ON(preempt_count() <= 0) and spamming the console constantly. This patch fix the issue by always calling {get,put}_buffers() since preempt_{disable,enable}() functions are nestable. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1323526/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
