From: Tejun Heo <tj@xxxxxxxxxx> Subject: memcg: css_alloc should return an ERR_PTR value on error 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 ]--- Link: http://lkml.kernel.org/r/20160621165740.GJ3262@xxxxxxxxxxxxxxx Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Reported-by: Johannes Weiner <hannes@xxxxxxxxxxx> Reviewed-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN mm/memcontrol.c~memcg-css_alloc-should-return-an-err_ptr-value-on-error mm/memcontrol.c --- a/mm/memcontrol.c~memcg-css_alloc-should-return-an-err_ptr-value-on-error +++ a/mm/memcontrol.c @@ -4203,7 +4203,7 @@ mem_cgroup_css_alloc(struct cgroup_subsy return &memcg->css; fail: mem_cgroup_free(memcg); - return NULL; + return ERR_PTR(-ENOMEM); } static int _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
