From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH net] bpf: cpumap: use GFP_KERNEL instead of GFP_ATOMIC in __cpu_map_entry_alloc() Date: Wed, 14 Feb 2018 16:06:40 +0100 Message-ID: <20180214150640.GC3443@dhcp22.suse.cz> References: <1518617854-4486-1-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, Matthew Wilcox , Jesper Dangaard Brouer , akpm@linux-foundation.org, dhowells@redhat.com, hannes@cmpxchg.org To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: <1518617854-4486-1-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed 14-02-18 22:17:34, Jason Wang wrote: > There're several implications after commit 0bf7800f1799 ("ptr_ring: > try vmalloc() when kmalloc() fails") with the using of vmalloc() since > can't allow GFP_ATOMIC but mandate GFP_KERNEL. This will lead a WARN > since cpumap try to call with GFP_ATOMIC. Fortunately, entry > allocation of cpumap can only be done through syscall path which means > GFP_ATOMIC is not necessary, so fixing this by replacing GFP_ATOMIC > with GFP_KERNEL. map_update_elem does the following. Unless I am missing something and the callback doesn't call cpu_map_update_elem there then we are in a non-preemptible context there and GFP_WAIT would blow up. rcu_read_lock(); err = map->ops->map_update_elem(map, key, value, attr->flags); rcu_read_unlock(); > Reported-by: syzbot+1a240cdb1f4cc88819df@syzkaller.appspotmail.com > Fixes: 0bf7800f1799 ("ptr_ring: try vmalloc() when kmalloc() fails") > Cc: Michal Hocko > Cc: Daniel Borkmann > Cc: Matthew Wilcox > Cc: Jesper Dangaard Brouer > Cc: akpm@linux-foundation.org > Cc: dhowells@redhat.com > Cc: hannes@cmpxchg.org > Signed-off-by: Jason Wang > --- > kernel/bpf/cpumap.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c > index fbfdada6..a4bb0b3 100644 > --- a/kernel/bpf/cpumap.c > +++ b/kernel/bpf/cpumap.c > @@ -334,7 +334,7 @@ static int cpu_map_kthread_run(void *data) > static struct bpf_cpu_map_entry *__cpu_map_entry_alloc(u32 qsize, u32 cpu, > int map_id) > { > - gfp_t gfp = GFP_ATOMIC|__GFP_NOWARN; > + gfp_t gfp = GFP_KERNEL | __GFP_NOWARN; > struct bpf_cpu_map_entry *rcpu; > int numa, err; > > -- > 2.7.4 -- Michal Hocko SUSE Labs