From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladimir Davydov Subject: Re: [PATCH] memcg: css_alloc should return an ERR_PTR value on error Date: Wed, 22 Jun 2016 19:44:12 +0300 Message-ID: <20160622164412.GD21652@esperanza> References: <20160621165740.GJ3262@mtj.duckdns.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=virtuozzo.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=9mV0FKOsCZrMpEI+5zeA7fIfxpp64x08WFkGMTEB9HA=; b=Tue/nbghX7B07Cvrs5nNHL6KVx7IbUuDxjsolSoEhDO61bDDOP5nAN53D+YYp1oz2NrVQtdWKPLApSkU+jRO1rPftFRW/4rzFsdbcLm4j4VGr9L6j0AjZxc89EimPiAatiSuRqe/3BpLpBNCOqrSo2incJay1jnbw/c3reFddVE= Content-Disposition: inline In-Reply-To: <20160621165740.GJ3262-qYNAdHglDFBN0TnZuCh8vA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Transfer-Encoding: 7bit To: Tejun Heo Cc: Andrew Morton , Johannes Weiner , Michal Hocko , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org On Tue, Jun 21, 2016 at 12:57:40PM -0400, 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: > [] dump_stack+0x68/0xa1 > [] warn_alloc_failed+0xd6/0x130 > [] __alloc_pages_nodemask+0x4c6/0xf20 > [] alloc_pages_current+0x66/0xe0 > [] alloc_kmem_pages+0x14/0x80 > [] kmalloc_order_trace+0x2a/0x1a0 > [] __kmalloc+0x291/0x310 > [] memcg_update_all_caches+0x6c/0x130 > [] mem_cgroup_css_alloc+0x590/0x610 > [] cgroup_apply_control_enable+0x18b/0x370 > [] cgroup_mkdir+0x1de/0x2e0 > [] kernfs_iop_mkdir+0x55/0x80 > [] vfs_mkdir+0xb9/0x150 > [] SyS_mkdir+0x66/0xd0 > [] do_syscall_64+0x53/0x120 > [] entry_SYSCALL64_slow_path+0x25/0x25 > ... > BUG: unable to handle kernel NULL pointer dereference at 00000000000000d0 > IP: [] 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:[] [] 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: > [] cgroup_apply_control_enable+0x1ac/0x370 > [] cgroup_mkdir+0x1de/0x2e0 > [] kernfs_iop_mkdir+0x55/0x80 > [] vfs_mkdir+0xb9/0x150 > [] SyS_mkdir+0x66/0xd0 > [] do_syscall_64+0x53/0x120 > [] 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 [] init_and_link_css+0x37/0x220 > RSP > CR2: 00000000000000d0 > ---[ end trace a2d8836ae1e852d1 ]--- > > Signed-off-by: Tejun Heo > Reported-by: Johannes Weiner > Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Reviewed-by: Vladimir Davydov > --- > 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