From mboxrd@z Thu Jan 1 00:00:00 1970 From: Igor Mammedov Subject: Re: [PATCH] memcg: do not expose uninitialized mem_cgroup_per_node to world Date: Thu, 09 Jun 2011 10:11:11 +0200 Message-ID: <4DF0801F.9050908__26233.8644861758$1307607208$gmane$org@redhat.com> References: <1306925044-2828-1-git-send-email-imammedo@redhat.com> <20110601123913.GC4266@tiehlicka.suse.cz> <4DE6399C.8070802@redhat.com> <20110601134149.GD4266@tiehlicka.suse.cz> <4DE64F0C.3050203@redhat.com> <20110601152039.GG4266@tiehlicka.suse.cz> <4DE66BEB.7040502@redhat.com> <4DE8D50F.1090406@redhat.com> <4DEE26E7.2060201@redhat.com> <20110608123527.479e6991.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20110608123527.479e6991.kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: KAMEZAWA Hiroyuki Cc: stefano.stabellini-mvvWK6WmYclDPfheJLI6IQ@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Michal Hocko , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, keir.xen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, Hiroyuki Kamezawa , Paul Menage , balbir-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org List-Id: containers.vger.kernel.org On 06/08/2011 05:35 AM, KAMEZAWA Hiroyuki wrote: > On Tue, 07 Jun 2011 15:25:59 +0200 > Igor Mammedov wrote: > >> Sorry for late reply, >> >> On 06/03/2011 03:00 PM, Hiroyuki Kamezawa wrote: >>> 2011/6/3 Igor Mammedov: >>>> On 06/02/2011 01:10 AM, Hiroyuki Kamezawa wrote: >>>>>> pc = list_entry(list->prev, struct page_cgroup, lru); >>>>> Hmm, I disagree your patch is a fix for mainline. At least, a cgroup >>>>> before completion of >>>>> create() is not populated to userland and you never be able to rmdir() >>>>> it because you can't >>>>> find it. >>>>> >>>>> >>>>> >26: e8 7d 12 30 00 call 0x3012a8 >>>>> >2b:* 8b 73 08 mov 0x8(%ebx),%esi<-- trapping >>>>> instruction >>>>> >2e: 8b 7c 24 24 mov 0x24(%esp),%edi >>>>> >32: 8b 07 mov (%edi),%eax >>>>> >>>>> Hm, what is the call 0x3012a8 ? >>>>> >>>> pc = list_entry(list->prev, struct page_cgroup, lru); >>>> if (busy == pc) { >>>> list_move(&pc->lru, list); >>>> busy = 0; >>>> spin_unlock_irqrestore(&zone->lru_lock, flags); >>>> continue; >>>> } >>>> spin_unlock_irqrestore(&zone->lru_lock, flags);<---- is >>>> call 0x3012a8 >>>> ret = mem_cgroup_move_parent(pc, mem, GFP_KERNEL); >>>> >>>> and mov 0x8(%ebx),%esi >>>> is dereferencing of 'pc' in inlined mem_cgroup_move_parent >>>> >>> Ah, thank you for input..then panicd at accessing pc->page and "pc" >>> was 0xfffffff4. >>> it means list->prev was NULL. >>> >> yes, that's the case. >>>> I've looked at vmcore once more and indeed there isn't any parallel task >>>> that touches cgroups code path. >>>> Will investigate if it is xen to blame for incorrect data in place. >>>> >>>> Thanks very much for your opinion. >>> What curious to me is that the fact "list->prev" is NULL. >>> I can see why you doubt the initialization code ....the list pointer never >>> contains NULL once it's used.... >>> it smells like memory corruption or some to me. If you have vmcore, >>> what the problematic mem_cgroup_per_zone(node) contains ? >> it has all zeros except for last field: >> >> crash> rd f3446a00 62 >> f3446a00: 00000000 00000000 00000000 00000000 ................ >> f3446a10: 00000000 00000000 00000000 00000000 ................ >> f3446a20: 00000000 00000000 00000000 00000000 ................ >> f3446a30: 00000000 00000000 00000000 00000000 ................ >> f3446a40: 00000000 00000000 00000000 00000000 ................ >> f3446a50: 00000000 00000000 00000000 00000000 ................ >> f3446a60: 00000000 00000000 00000000 00000000 ................ >> f3446a70: 00000000 00000000 f36ef800 f3446a7c ..........n.|jD. >> f3446a80: f3446a7c f3446a84 f3446a84 f3446a8c |jD..jD..jD..jD. >> f3446a90: f3446a8c f3446a94 f3446a94 f3446a9c .jD..jD..jD..jD. >> f3446aa0: f3446a9c 00000000 00000000 00000000 .jD............. >> f3446ab0: 00000000 00000000 00000000 00000000 ................ >> f3446ac0: 00000000 00000000 00000000 00000000 ................ >> f3446ad0: 00000000 00000000 00000000 00000000 ................ >> f3446ae0: 00000000 00000000 00000000 00000000 ................ >> f3446af0: 00000000 f36ef800 >> >> crash> struct mem_cgroup f36ef800 >> struct mem_cgroup { >> ... >> info = { >> nodeinfo = {0xf3446a00} >> }, >> ... >> >> It looks like a very targeted corruption of the first zone except of >> the last field, while the second zone and the rest are perfectly >> normal (i.e. have empty initialized lists). >> > Hmm, ok, thank you. Then, mem_cgroup_pre_zone[] was initialized once. > In this kind of case, I tend to check slab header of memory object f3446a00, > or check whether f3446a00 is an alive slab object or not. It looks like f3446a00 alive/allocated object crash> kmem f3446a00 CACHE NAME OBJSIZE ALLOCATED TOTAL SLABS SSIZE f7000c80 size-512 512 2251 2616 327 4k SLAB MEMORY TOTAL ALLOCATED FREE f3da6540 f3446000 8 1 7 FREE / [ALLOCATED] [f3446a00] PAGE PHYSICAL MAPPING INDEX CNT FLAGS c1fa58c0 33446000 0 70 1 2800080 However I have a related crash that can lead to not initialized lists of the first entry (i.e. to what we see at f3446a00), debug kernel sometimes will crash at alloc_mem_cgroup_per_zone_info: XXX: pn: f208dc00, phy: 3208dc00 XXX: pn: f2e85a00, phy: 32e85a00 BUG: unable to handle kernel paging request at 9b74e240 IP: [] mem_cgroup_create0x+0xef/0x350 *pdpt = 0000000033542001 *pde = 0000000000000000 Oops: 0002 [#1] SMP ... Pid: 1823, comm: libvirtd Tainted: G ---------------- T (2.6.32.700565 #21) HVM domU EIP: 0060:[] EFLAGS: 00210297 CPU: 3 EIP is at mem_cgroup_create+0xef/0x350 EAX: 9b74e240 EBX: f2e85a00 ECX: 00000001 EDX: 00000001 ESI: a88c8840 EDI: a88c8840 EBP: f201deb4 ESP: f201de8c DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 Process libvirtd (pid: 1823, ti=f201c000 task=f3642ab0 task.ti=f201c000) Stack: c09579b2 f2e85a00 32e85a00 f3455800 00000000 f2e85a00 f2c14ac0 c0a5a820 <0> fffffff4 f2c14ac0 f201def8 c049d3a7 00000000 00000000 00000000 000001ed <0> f2c14ac8 f5fa4400 f24fe954 f3502000 f2c14e40 f24f5608 f3502010 f2c14ac0 Call Trace: [] cgroup_mkdir+0xf7/0x450 [] vfs_mkdir+0x93/0xf0 [] ? lookup_hash+0x27/0x30 [] sys_mkdirat+0xde/0x100 [] ? call_rcu_sched+0xd/0x10 [] ? call_rcu+0x8/0x10 [] ? __put_cred+0x2f/0x50 [] ? sys_faccessat+0x14d/0x180 [] ? filp_close+0x47/0x70 [] sys_mkdir+0x20/0x30 [] sysenter_do_call+0x12/0x28 static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node) { ... memset(pn, 0, sizeof(*pn)); for (zone = 0; zone< MAX_NR_ZONES; zone++) { mz =&pn->zoneinfo[zone]; for_each_lru(l) INIT_LIST_HEAD(&mz->lists[l]);<- crash here mz->usage_in_excess = 0; mz->on_tree = false; mz->mem = mem; } ... crash> dis 0xc080b93e 15 0xc080b93e: movl $0x0,-0x18(%ebp) 0xc080b945: mov %esi,-0x1c(%ebp) 0xc080b948: imul $0x7c,-0x18(%ebp),%edi 0xc080b94c: xor %ecx,%ecx 0xc080b94e: xor %edx,%edx 0xc080b950: lea (%edi,%edx,8),%esi 0xc080b953: add $0x1,%ecx 0xc080b956: lea (%ebx,%esi,1),%eax 0xc080b959: add $0x1,%edx 0xc080b95c: cmp $0x5,%ecx 0xc080b95f: mov %eax,(%ebx,%esi,1) 0xc080b962: mov %eax,0x4(%eax) 0xc080b965: jne 0xc080b950 0xc080b967: mov -0x14(%ebp),%eax 0xc080b96a: movl $0x0,0x6c(%eax) EDI on the first iteration should be 0 however it is a88c8840 according to Oops dump and looking at -0x18(%ebp) in core shows 0 as it should be: crash> x/xw 0xf201deb4-0x18 0xf201de9c: 0x00000000 so it looks like EDI is incorrectly restored by Xen or at the moment when 0xc080b948 was executed -0x18(%ebp) had that weird value. It is possible that invalid EDI value and following 0xc080b950: lea (%edi,%edx,8),%esi lead to some accessible page and writes 0xc080b95f: mov %eax,(%ebx,%esi,1) 0xc080b962: mov %eax,0x4(%eax) silently go to that page. Than after init lists loop it uses correct pn offset from -0x14(%ebp) and initialises the rest fields of structure on the correct page. mz->usage_in_excess = 0; mz->on_tree = false; mz->mem = mem; 0xc080b967: mov -0x14(%ebp),%eax<- 0xc080b96a: movl $0x0,0x6c(%eax) 0xc080b971: movl $0x0,0x70(%eax) 0xc080b978: movb $0x0,0x74(%eax) 0xc080b97c: mov -0x1c(%ebp),%edx 0xc080b97f: mov %edx,0x78(%eax) 0xc080b982: add $0x7c,%eax 0xc080b985: addl $0x1,-0x18(%ebp) 0xc080b989: cmpl $0x4,-0x18(%ebp) 0xc080b98d: mov %eax,-0x14(%ebp) 0xc080b990: jne 0xc080b948 which could lead to the 0-ed list entries of the first zone and the originally reported Oops in mem_cgroup_force_empty. Afterwards it looks like: 0xc080b985: addl $0x1,-0x18(%ebp) -0x18(%ebp) is read correctly and the rest of 3 mz entries are initialized as expected. So question is why and how 0xc080b948: imul $0x7c,-0x18(%ebp),%edi may be screwed up PS: However, memory search for the went astray writes of the first entry i.e. sequesnce f3446a00 f3446a00 in a couple of vmcores didn't give any positive results. > Thanks, > -Kame >> PS: >> It most easily reproduced only on xen hvm 32bit guest under heavy >> vcpus contention for real cpus resources (i.e. I had to overcommit >> cpus and run several cpu hog tasks on host to make guest crash on >> reboot cycle). >> And from last experiments, crash happens only on on hosts that >> doesn't have hap feature or if hap is disabled in hypervisor. >> >>> Thanks, >>> -Kame >>