Messages in this thread | | | Subject | Re: WARNING in kvmalloc_node | From | Jason Wang <> | Date | Wed, 14 Feb 2018 20:02:27 +0800 |
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On 2018年02月14日 19:51, Michal Hocko wrote: > On Wed 14-02-18 19:47:30, Jason Wang wrote: >> >> On 2018年02月14日 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: >>>> [...] >>>>>> kvmalloc include/linux/mm.h:541 [inline] >>>>>> kvmalloc_array include/linux/mm.h:557 [inline] >>>>>> __ptr_ring_init_queue_alloc include/linux/ptr_ring.h:474 [inline] >>>>>> ptr_ring_init include/linux/ptr_ring.h:492 [inline] >>>>>> __cpu_map_entry_alloc kernel/bpf/cpumap.c:359 [inline] >>>>>> cpu_map_update_elem+0x3c3/0x8e0 kernel/bpf/cpumap.c:490 >>>>>> 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().
Thanks
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