[CC Andrey] On Sat 31-03-18 13:47:05, syzbot wrote: > Hello, > > syzbot hit the following crash on upstream commit > 9dd2326890d89a5179967c947dab2bab34d7ddee (Fri Mar 30 17:29:47 2018 +0000) > Merge tag 'ceph-for-4.16-rc8' of git://github.com/ceph/ceph-client > syzbot dashboard link: > https://syzkaller.appspot.com/bug?extid=8a5de3cce7cdc70e9ebe > > So far this crash happened 14 times on upstream. > C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5578311367393280 > syzkaller reproducer: > https://syzkaller.appspot.com/x/repro.syz?id=5708657048158208 > Raw console output: > https://syzkaller.appspot.com/x/log.txt?id=6693821748346880 > Kernel config: > https://syzkaller.appspot.com/x/.config?id=-2760467897697295172 > compiler: gcc (GCC) 7.1.1 20170620 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+8a5de3cce7cdc70e9ebe@xxxxxxxxxxxxxxxxxxxxxxxxx > It will help syzbot understand when the bug is fixed. See footer for > details. > If you forward the report, please keep this part and the footer. > > RBP: 00000000006dcc20 R08: 0000000000000002 R09: 0000000000003335 > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e > R13: 00007f1747954d80 R14: ffffffffffffffff R15: 0000000000000006 > kasan: CONFIG_KASAN_INLINE enabled > kasan: GPF could be caused by NULL-ptr deref or user memory access > general protection fault: 0000 [#1] SMP KASAN > Dumping ftrace buffer: > (ftrace buffer empty) > Modules linked in: > CPU: 0 PID: 4422 Comm: syzkaller101598 Not tainted 4.16.0-rc7+ #372 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > RIP: 0010:free_mem_cgroup_per_node_info mm/memcontrol.c:4111 [inline] > RIP: 0010:__mem_cgroup_free+0x71/0x110 mm/memcontrol.c:4120 Is this a real bug or a KASAN false positive? The RIP points at free_percpu(pn->lruvec_stat_cpu); Which can be NULL if we are failing to allocate per-node data in mem_cgroup_alloc. You stack unwinder seems to point to mem_cgroup_css_alloc->mem_cgroup_free though and that one cannot see NULL memcg->nodeinfo[node] AFAICS. Even if this is really mem_cgroup_alloc path then calling free_percpu with NULL pointer should be OK. Or am I missing something? > RSP: 0018:ffff8801accf75a8 EFLAGS: 00010206 > RAX: 0000000000000011 RBX: 0000000000000000 RCX: ffffffff8310cdfd > RDX: 0000000000000000 RSI: 0000000000000040 RDI: 0000000000000088 > RBP: ffff8801accf75c8 R08: 0000000000000000 R09: ffff8801accf73a0 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: ffff8801ad210d40 R14: dffffc0000000000 R15: ffff8801ad210d40 > FS: 00007f1747955700(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000460000 CR3: 00000001cb367004 CR4: 00000000001606f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > mem_cgroup_free mm/memcontrol.c:4128 [inline] > mem_cgroup_css_alloc+0x403/0x19c0 mm/memcontrol.c:4239 > css_create kernel/cgroup/cgroup.c:4729 [inline] > cgroup_apply_control_enable+0x44d/0xbc0 kernel/cgroup/cgroup.c:2916 > cgroup_mkdir+0x56f/0xfc0 kernel/cgroup/cgroup.c:4938 > kernfs_iop_mkdir+0x153/0x1e0 fs/kernfs/dir.c:1099 > vfs_mkdir+0x390/0x600 fs/namei.c:3800 > SYSC_mkdirat fs/namei.c:3823 [inline] > SyS_mkdirat+0x22b/0x2b0 fs/namei.c:3807 > do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x42/0xb7 > RIP: 0033:0x44a0c9 > RSP: 002b:00007f1747954d78 EFLAGS: 00000246 ORIG_RAX: 0000000000000102 > RAX: ffffffffffffffda RBX: 00000000006dcc24 RCX: 000000000044a0c9 > RDX: 0000000000000020 RSI: 0000000020000280 RDI: 0000000000000005 > RBP: 00000000006dcc20 R08: 0000000000000002 R09: 0000000000003335 > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e > R13: 00007f1747954d80 R14: ffffffffffffffff R15: 0000000000000006 > Code: 00 00 48 89 f8 48 c1 e8 03 42 80 3c 30 00 0f 85 99 00 00 00 4f 8b a4 > e5 f0 09 00 00 49 8d bc 24 88 00 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 30 00 > 0f 85 88 00 00 00 49 8b bc 24 88 00 00 00 e8 77 > RIP: free_mem_cgroup_per_node_info mm/memcontrol.c:4111 [inline] RSP: > ffff8801accf75a8 > RIP: __mem_cgroup_free+0x71/0x110 mm/memcontrol.c:4120 RSP: ffff8801accf75a8 > ---[ end trace 57ac07c30502ef78 ]--- > Kernel panic - not syncing: Fatal exception -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
