On Tue 21-06-16 12:57:40, Tejun Heo wrote: > mem_cgroup_css_alloc() was returning NULL on failure while cgroup core > expected it to return an ERR_PTR value leading to the following NULL > deref after a css allocation failure. Fix it by return > ERR_PTR(-ENOMEM) instead. I'll also update cgroup core so that it > can handle NULL returns. > > mkdir: page allocation failure: order:6, mode:0x240c0c0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO) > CPU: 0 PID: 8738 Comm: mkdir Not tainted 4.7.0-rc3+ #123 > ... > Call Trace: > [<ffffffff81321937>] dump_stack+0x68/0xa1 > [<ffffffff811522f6>] warn_alloc_failed+0xd6/0x130 > [<ffffffff81152816>] __alloc_pages_nodemask+0x4c6/0xf20 > [<ffffffff8119df86>] alloc_pages_current+0x66/0xe0 > [<ffffffff81153564>] alloc_kmem_pages+0x14/0x80 > [<ffffffff811705ca>] kmalloc_order_trace+0x2a/0x1a0 > [<ffffffff811a7a61>] __kmalloc+0x291/0x310 > [<ffffffff811718dc>] memcg_update_all_caches+0x6c/0x130 > [<ffffffff818d0290>] mem_cgroup_css_alloc+0x590/0x610 > [<ffffffff810f4c7b>] cgroup_apply_control_enable+0x18b/0x370 > [<ffffffff810f8afe>] cgroup_mkdir+0x1de/0x2e0 > [<ffffffff8123cf35>] kernfs_iop_mkdir+0x55/0x80 > [<ffffffff811c6599>] vfs_mkdir+0xb9/0x150 > [<ffffffff811cc666>] SyS_mkdir+0x66/0xd0 > [<ffffffff81002df3>] do_syscall_64+0x53/0x120 > [<ffffffff818d719a>] entry_SYSCALL64_slow_path+0x25/0x25 > ... > BUG: unable to handle kernel NULL pointer dereference at 00000000000000d0 > IP: [<ffffffff810f2ca7>] init_and_link_css+0x37/0x220 > PGD 34b1e067 PUD 3a109067 PMD 0 > Oops: 0002 [#1] SMP > Modules linked in: > CPU: 0 PID: 8738 Comm: mkdir Not tainted 4.7.0-rc3+ #123 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.2-20160422_131301-anatol 04/01/2014 > task: ffff88007cbc5200 ti: ffff8800666d4000 task.ti: ffff8800666d4000 > RIP: 0010:[<ffffffff810f2ca7>] [<ffffffff810f2ca7>] init_and_link_css+0x37/0x220 > RSP: 0018:ffff8800666d7d90 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 > RDX: ffffffff810f2499 RSI: 0000000000000000 RDI: 0000000000000008 > RBP: ffff8800666d7db8 R08: 0000000000000003 R09: 0000000000000000 > R10: 0000000000000001 R11: 0000000000000000 R12: ffff88005a5fb400 > R13: ffffffff81f0f8a0 R14: ffff88005a5fb400 R15: 0000000000000010 > FS: 00007fc944689700(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f3aed0d2b80 CR3: 000000003a1e8000 CR4: 00000000000006f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Stack: > ffffffff81f0f8a0 ffffffff81f0f8a0 ffff88005a5fb400 0000000000000000 > ffff88005a5fb400 ffff8800666d7e18 ffffffff810f4c9c ffff88005a5fb400 > ffffffff82d23470 ffff88007cbc57f0 ffff88007cbc5200 ffff88007d013000 > Call Trace: > [<ffffffff810f4c9c>] cgroup_apply_control_enable+0x1ac/0x370 > [<ffffffff810f8afe>] cgroup_mkdir+0x1de/0x2e0 > [<ffffffff8123cf35>] kernfs_iop_mkdir+0x55/0x80 > [<ffffffff811c6599>] vfs_mkdir+0xb9/0x150 > [<ffffffff811cc666>] SyS_mkdir+0x66/0xd0 > [<ffffffff81002df3>] do_syscall_64+0x53/0x120 > [<ffffffff818d719a>] entry_SYSCALL64_slow_path+0x25/0x25 > Code: 89 f5 48 89 fb 49 89 d4 48 83 ec 08 8b 05 72 3b d8 00 85 c0 0f 85 60 01 00 00 4c 89 e7 e8 72 f7 ff ff 48 8d 7b 08 48 89 d9 31 c0 <48> c7 83 d0 00 00 00 00 00 00 00 48 83 e7 f8 48 29 f9 81 c1 d8 > RIP [<ffffffff810f2ca7>] init_and_link_css+0x37/0x220 > RSP <ffff8800666d7d90> > CR2: 00000000000000d0 > ---[ end trace a2d8836ae1e852d1 ]--- > > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> > Reported-by: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx Acked-by: Michal Hocko <mhocko@xxxxxxxx> I have tried to track down since when we are broken but it seems that it's for a long time. I got back to 2007 and ddbcc7e8e50ae and gave up. Thanks! > --- > mm/memcontrol.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 75e7440..fbb8ba6 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4203,7 +4203,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) > return &memcg->css; > fail: > mem_cgroup_free(memcg); > - return NULL; > + return ERR_PTR(-ENOMEM); > } > > static int -- 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
