Messages in this thread | | | Date | Thu, 19 Jul 2012 12:44:07 -0400 | From | Neil Horman <> | Subject | Re: [PATCH] net, cgroup: Fix boot failure due to iteration of uninitialized list |
| |
On Thu, Jul 19, 2012 at 09:57:37PM +0530, Srivatsa S. Bhat wrote: > After commit ef209f15 (net: cgroup: fix access the unallocated memory in > netprio cgroup), boot fails with the following NULL pointer dereference: > > Initializing cgroup subsys devices > Initializing cgroup subsys freezer > Initializing cgroup subsys net_cls > Initializing cgroup subsys blkio > Initializing cgroup subsys perf_event > Initializing cgroup subsys net_prio > BUG: unable to handle kernel NULL pointer dereference at 0000000000000698 > IP: [<ffffffff8145e8d6>] cgrp_create+0xf6/0x190 > PGD 0 > Oops: 0000 [#1] SMP > CPU 0 > Modules linked in: > > Pid: 0, comm: swapper/0 Not tainted 3.5.0-rc7-mandeep #1 IBM IBM System x -[7870C4Q]-/68Y8033 > RIP: 0010:[<ffffffff8145e8d6>] [<ffffffff8145e8d6>] cgrp_create+0xf6/0x190 > RSP: 0000:ffffffff81a01ea8 EFLAGS: 00010213 > RAX: 0000000000000000 RBX: ffffffffffffff10 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: 0000000000000246 RDI: ffffffff81aa70a0 > RBP: ffffffff81a01ed8 R08: 0000000000000000 R09: 0000000000000000 > R10: ffff8808ff8641c0 R11: 6e697a696c616974 R12: 0000000000000001 > R13: ffff8808ff8641c0 R14: 0000000000000000 R15: 0000000000093970 > FS: 0000000000000000(0000) GS:ffff8808ffc00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > CR2: 0000000000000698 CR3: 0000000001a0b000 CR4: 00000000000006b0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > Process swapper/0 (pid: 0, threadinfo ffffffff81a00000, task ffffffff81a13420) > Stack: > ffffffff81a01eb8 ffffffff818060ff ffffffff81d75ec8 ffffffff81aa8960 > ffffffff81aa8960 ffffffff81b4c2c0 ffffffff81a01ef8 ffffffff81b1cb78 > 0000000000000018 0000000000000048 ffffffff81a01f18 ffffffff81b1ce13 > Call Trace: > [<ffffffff81b1cb78>] cgroup_init_subsys+0x83/0x169 > [<ffffffff81b1ce13>] cgroup_init+0x36/0x119 > [<ffffffff81affef7>] start_kernel+0x3ba/0x3ef > [<ffffffff81aff95b>] ? kernel_init+0x27b/0x27b > [<ffffffff81aff356>] x86_64_start_reservations+0x131/0x136 > [<ffffffff81aff45e>] x86_64_start_kernel+0x103/0x112 > Code: 01 48 3d f8 e1 ec 81 48 8d 98 10 ff ff ff 75 1b eb 73 0f 1f 00 48 8b 83 f0 00 00 00 48 3d f8 e1 ec 81 48 8d 98 10 ff ff ff 74 5a <48> 8b 83 88 07 00 00 48 85 c0 74 de 44 3b 60 10 76 d8 44 89 e6 > RIP [<ffffffff8145e8d6>] cgrp_create+0xf6/0x190 > RSP <ffffffff81a01ea8> > CR2: 0000000000000698 > ---[ end trace a7919e7f17c0a725 ]--- > Kernel panic - not syncing: Attempted to kill the idle task! > > The code corresponds to: > > update_netdev_tables(): > for_each_netdev(&init_net, dev) { > map = rtnl_dereference(dev->priomap); <---- HERE > > > The list head is initialized in netdev_init(), which is called much > later than cgrp_create(). So the problem is that we are calling > update_netdev_tables() way too early (in cgrp_create()), which will > end up traversing the not-yet-circular linked list. So at some point, > the dev pointer will become NULL and hence dev->priomap becomes an > invalid access. > > To fix this, just remove the update_netdev_tables() function entirely, > since it appears that write_update_netdev_table() will handle things > just fine. > > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> > --- > > Requesting a thorough review of this patch, since I am not sure whether > removing update_netdev_tables() is perfectly OK and whether that is the > right thing to do. > We could do this I suppose, but this has already been fixed by 734b65417b24d6eea3e3d7457e1f11493890ee1d >
| |