From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f72.google.com (mail-vk0-f72.google.com [209.85.213.72]) by kanga.kvack.org (Postfix) with ESMTP id D42D46B0006 for ; Wed, 14 Feb 2018 16:24:13 -0500 (EST) Received: by mail-vk0-f72.google.com with SMTP id y144so14105063vky.14 for ; Wed, 14 Feb 2018 13:24:13 -0800 (PST) Received: from www62.your-server.de (www62.your-server.de. [213.133.104.62]) by mx.google.com with ESMTPS id j18si2717991wre.473.2018.02.14.04.17.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 14 Feb 2018 04:17:27 -0800 (PST) Subject: Re: WARNING in kvmalloc_node References: <001a1144c4ca5dc9d6056520c7b7@google.com> <20180214025533.GA28811@bombadil.infradead.org> <20180214084308.GX3443@dhcp22.suse.cz> <24351362-a099-3317-2b96-8cdc6835eb1e@redhat.com> <20180214115119.GA3443@dhcp22.suse.cz> <62489a86-b578-b075-3ada-c2f5baf5b787@redhat.com> From: Daniel Borkmann Message-ID: Date: Wed, 14 Feb 2018 13:17:18 +0100 MIME-Version: 1.0 In-Reply-To: <62489a86-b578-b075-3ada-c2f5baf5b787@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Jason Wang , Michal Hocko Cc: Matthew Wilcox , syzbot , akpm@linux-foundation.org, dhowells@redhat.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mingo@kernel.org, rppt@linux.vnet.ibm.com, syzkaller-bugs@googlegroups.com, vbabka@suse.cz, viro@zeniv.linux.org.uk, Alexei Starovoitov , netdev@vger.kernel.org, brouer@redhat.com, "Michael S. Tsirkin" On 02/14/2018 01:02 PM, Jason Wang wrote: > On 2018a1'02ae??14ae?JPY 19:51, Michal Hocko wrote: >> On Wed 14-02-18 19:47:30, Jason Wang wrote: >>> On 2018a1'02ae??14ae?JPY 17:28, Daniel Borkmann wrote: >>>> [ +Jason, +Jesper ] >>>> >>>> On 02/14/2018 09:43 AM, Michal Hocko wrote: >>>>> On Tue 13-02-18 18:55:33, Matthew Wilcox wrote: >>>>>> On Tue, Feb 13, 2018 at 03:59:01PM -0800, syzbot wrote: >>>>> [...] >>>>>>> A A kvmalloc include/linux/mm.h:541 [inline] >>>>>>> A A kvmalloc_array include/linux/mm.h:557 [inline] >>>>>>> A A __ptr_ring_init_queue_alloc include/linux/ptr_ring.h:474 [inline] >>>>>>> A A ptr_ring_init include/linux/ptr_ring.h:492 [inline] >>>>>>> A A __cpu_map_entry_alloc kernel/bpf/cpumap.c:359 [inline] >>>>>>> A A cpu_map_update_elem+0x3c3/0x8e0 kernel/bpf/cpumap.c:490 >>>>>>> A A map_update_elem kernel/bpf/syscall.c:698 [inline] >>>>>> Blame the BPF people, not the MM people ;-) >>>> Heh, not really. ;-) >>>> >>>>> Yes. kvmalloc (the vmalloc part) doesn't support GFP_ATOMIC semantic. >>>> Agree, that doesn't work. >>>> >>>> Bug was added in commit 0bf7800f1799 ("ptr_ring: try vmalloc() when kmalloc() fails"). >>>> >>>> Jason, please take a look at fixing this, thanks! >>> It looks to me the only solution is to revert that commit. >> Do you really need this to be GFP_ATOMIC? I can see some callers are >> under RCU read lock but can we perhaps do the allocation outside of this >> section? > > If I understand the code correctly, the code would be called by XDP program (usually run inside a bh) which makes it hard to do this. > > Rethink of this, we can probably test gfp and not call kvmalloc if GFP_ATOMIC is set in __ptr_ring_init_queue_alloc(). That would be one option indeed (probably useful in any case to make the API more robust). Another one is to just not use GFP_ATOMIC in cpumap. Looking at it, update can neither be called out of a BPF prog since prevented by verifier nor under RCU reader side when updating this type of map from syscall path. Jesper, any concrete reason we still need GFP_ATOMIC here? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org