Messages in this thread | | | Subject | Re: WARNING in kvmalloc_node | From | Jason Wang <> | Date | Wed, 14 Feb 2018 20:47:56 +0800 |
| |
On 2018年02月14日 20:29, Jesper Dangaard Brouer wrote: > On Wed, 14 Feb 2018 13:17:18 +0100 > Daniel Borkmann <daniel@iogearbox.net> wrote: > >> On 02/14/2018 01:02 PM, Jason Wang wrote: >>> 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(). >> 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? > Allocations in cpumap (related to ptr_ring) should only be possible to > be initiated through userspace via bpf-syscall.
I see verifier guarantees this.
> Thus, there isn't any > reason for GFP_ATOMIC here. >
Want me to send a patch to remove GFP_ATOMIC here?
Thanks
| |