From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Serge E. Hallyn" Subject: Re: cgroup: BUG: unable to handle kernel NULL pointer dereference Date: Sat, 2 Jan 2016 12:24:16 -0600 Message-ID: <20160102182416.GA3957@mail.hallyn.com> References: <20160101234028.GA1750@hudson.localdomain> <20160102115437.GE3660@htj.duckdns.org> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20160102115437.GE3660-piEFEHQLUPpN0TnZuCh8vA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo Cc: Jeremiah Mahler , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Serge Hallyn , Stephen Rothwell , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Dan Williams On Sat, Jan 02, 2016 at 06:54:37AM -0500, Tejun Heo wrote: > On Fri, Jan 01, 2016 at 03:40:28PM -0800, Jeremiah Mahler wrote: > > all, > > > > When running the latest linux-next (20151231) two of my machines > > hang early in the boot sequence. The initial message is for a > > NULL pointer dereference. > > > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000030 > > > > And the RIP line refers to cgroup_path. > > > > RIP [] cgroup_path+0x30/0x80 > > > > Attached are pictures of the back trace. > > > > Let me know if I can do anything else to help. I will investigate the > > problem further if I get a chance. > > This is most likely from the recent changes from cgroup ns support. > Reverted the patchset for now as it also introduced a bisectability > issue. Serge, can you please look into this one? Tried to reproduce with setting CONFIG_CFQ_GROUP_IOSCHED=y, but did not succeed. Could you send me the .config? Also, if someone could send the objdump -d output that might help. Though really, it seems clear that current->nsproxy must be NULL. Hm, that's right - we used to have that issue in pidns (or was it netns) during process exit. I don't know that I'll get time this afternoon, but I'll look into it asap. thanks.