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Message-ID: <6e4e767a-3e83-c6e2-b5bf-b82ec1770e62@oracle.com> Date: Wed, 29 Aug 2018 17:21:35 -0700 From: Tushar Dave <tushar.n.dave@...cle.com> To: john.fastabend@...il.com, ast@...nel.org, daniel@...earbox.net, davem@...emloft.net, netdev@...r.kernel.org Cc: sowmini.varadhan@...cle.com Subject: Re: [PATCH net] ebpf: fix bpf_msg_pull_data On 08/29/2018 05:07 PM, Tushar Dave wrote: > While doing some preliminary testing it is found that bpf helper > bpf_msg_pull_data does not calculate the data and data_end offset > correctly. Fix it! > > Fixes: 015632bb30da ("bpf: sk_msg program helper bpf_sk_msg_pull_data") > Signed-off-by: Tushar Dave <tushar.n.dave@...cle.com> > Acked-by: Sowmini Varadhan <sowmini.varadhan@...cle.com> > --- > net/core/filter.c | 38 +++++++++++++++++++++++++------------- > 1 file changed, 25 insertions(+), 13 deletions(-) > > diff --git a/net/core/filter.c b/net/core/filter.c > index c25eb36..3eeb3d6 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -2285,7 +2285,7 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff *msg) > BPF_CALL_4(bpf_msg_pull_data, > struct sk_msg_buff *, msg, u32, start, u32, end, u64, flags) > { > - unsigned int len = 0, offset = 0, copy = 0; > + unsigned int len = 0, offset = 0, copy = 0, off = 0; > struct scatterlist *sg = msg->sg_data; > int first_sg, last_sg, i, shift; > unsigned char *p, *to, *from; > @@ -2299,22 +2299,30 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff *msg) > i = msg->sg_start; > do { > len = sg[i].length; > - offset += len; > if (start < offset + len) > break; > + offset += len; > i++; > if (i == MAX_SKB_FRAGS) > i = 0; > - } while (i != msg->sg_end); > + } while (i <= msg->sg_end); > > + /* return error if start is out of range */ > if (unlikely(start >= offset + len)) > return -EINVAL; > > - if (!msg->sg_copy[i] && bytes <= len) > - goto out; > + /* return error if i is last entry in sglist and end is out of range */ > + if (msg->sg_copy[i] && end > offset + len) > + return -EINVAL; > > first_sg = i; > > + /* if i is not last entry in sg list and end (i.e start + bytes) is > + * within this sg[i] then goto out and calculate data and data_end > + */ > + if (!msg->sg_copy[i] && end <= offset + len) > + goto out; > + > /* At this point we need to linearize multiple scatterlist > * elements or a single shared page. Either way we need to > * copy into a linear buffer exclusively owned by BPF. Then > @@ -2330,9 +2338,14 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff *msg) > i++; > if (i == MAX_SKB_FRAGS) > i = 0; > - if (bytes < copy) > + if (end < copy) > break; > - } while (i != msg->sg_end); > + } while (i <= msg->sg_end); > + > + /* return error if i is last entry in sglist and end is out of range */ > + if (i > msg->sg_end && end > offset + copy) > + return -EINVAL; > + > last_sg = i; > > if (unlikely(copy < end - start)) > @@ -2342,23 +2355,22 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff *msg) > if (unlikely(!page)) > return -ENOMEM; > p = page_address(page); > - offset = 0; > > i = first_sg; > do { > from = sg_virt(&sg[i]); > len = sg[i].length; > - to = p + offset; > + to = p + off; > > memcpy(to, from, len); > - offset += len; > + off += len; > sg[i].length = 0; > put_page(sg_page(&sg[i])); > > i++; > if (i == MAX_SKB_FRAGS) > i = 0; > - } while (i != last_sg); > + } while (i < last_sg); > > sg[first_sg].length = copy; > sg_set_page(&sg[first_sg], page, copy, 0); > @@ -2380,7 +2392,7 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff *msg) > else > move_from = i + shift; > > - if (move_from == msg->sg_end) > + if (move_from > msg->sg_end) > break; > > sg[i] = sg[move_from]; > @@ -2396,7 +2408,7 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff *msg) > if (msg->sg_end < 0) > msg->sg_end += MAX_SKB_FRAGS; > out: > - msg->data = sg_virt(&sg[i]) + start - offset; > + msg->data = sg_virt(&sg[first_sg]) + start - offset; > msg->data_end = msg->data + bytes; > > return 0; > Please discard this patch. I just noticed that Daniel Borkmann sent some similar fixes for bpf_msg_pull_data. -Tushar
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