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Date: Wed, 2 Feb 2022 13:43:53 +0800 From: htbegin <hotforest@...il.com> To: Daniel Borkmann <daniel@...earbox.net> Cc: Alexei Starovoitov <ast@...nel.org>, Martin KaFai Lau <kafai@...com>, Yonghong Song <yhs@...com>, Andrii Nakryiko <andrii@...nel.org>, "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, John Fastabend <john.fastabend@...il.com>, netdev@...r.kernel.org, bpf@...r.kernel.org, Hou Tao <houtao1@...wei.com> Subject: Re: [PATCH bpf-next] bpf: use VM_MAP instead of VM_ALLOC for ringbuf Hi, On Tue, Feb 1, 2022 at 10:25 AM htbegin <hotforest@...il.com> wrote: > > Hi, > > On Tue, Feb 1, 2022 at 12:28 AM Daniel Borkmann <daniel@...earbox.net> wrote: > > > > On 1/31/22 12:46 PM, Hou Tao wrote: > > > Now the ringbuf area in /proc/vmallocinfo is showed as vmalloc, > > > but VM_ALLOC is only used for vmalloc(), and for the ringbuf area > > > it is created by mapping allocated pages, so use VM_MAP instead. > > > > > > After the change, ringbuf info in /proc/vmallocinfo will changed from: > > > [start]-[end] 24576 ringbuf_map_alloc+0x171/0x290 vmalloc user > > > to > > > [start]-[end] 24576 ringbuf_map_alloc+0x171/0x290 vmap user > > > > Could you elaborate in the commit msg if this also has some other internal > > effect aside from the /proc/vmallocinfo listing? Thanks! > > > For now, the VM_MAP flag only affects the output in /proc/vmallocinfo. Just find out that the VM_ALLOC will be used to check whether or not the mapped area needs to be marked as accessible by commit 2fd3fb0be1d1 ("kasan, vmalloc: unpoison VM_ALLOC pages after mapping"). And the patch can fix the vmalloc oob access reported by syzbot [1] , I will post v2 to illustrate that. Regards, Tao [1]: https://lore.kernel.org/bpf/0000000000000a9b7d05d6ee565f@google.com/T/#u > > Thanks, > Tao > > > Signed-off-by: Hou Tao <houtao1@...wei.com> > > > --- > > > kernel/bpf/ringbuf.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c > > > index 638d7fd7b375..710ba9de12ce 100644 > > > --- a/kernel/bpf/ringbuf.c > > > +++ b/kernel/bpf/ringbuf.c > > > @@ -104,7 +104,7 @@ static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node) > > > } > > > > > > rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages, > > > - VM_ALLOC | VM_USERMAP, PAGE_KERNEL); > > > + VM_MAP | VM_USERMAP, PAGE_KERNEL); > > > if (rb) { > > > kmemleak_not_leak(pages); > > > rb->pages = pages; > > > > >
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