From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: [PATCH bpf 3/3] bpf: fix sg shift repair start offset in bpf_msg_pull_data Date: Wed, 29 Aug 2018 16:50:36 +0200 Message-ID: <20180829145036.5514-4-daniel@iogearbox.net> References: <20180829145036.5514-1-daniel@iogearbox.net> Cc: john.fastabend@gmail.com, netdev@vger.kernel.org, Daniel Borkmann To: alexei.starovoitov@gmail.com Return-path: Received: from www62.your-server.de ([213.133.104.62]:57295 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727537AbeH2SsJ (ORCPT ); Wed, 29 Aug 2018 14:48:09 -0400 In-Reply-To: <20180829145036.5514-1-daniel@iogearbox.net> Sender: netdev-owner@vger.kernel.org List-ID: When we perform the sg shift repair for the scatterlist ring, we currently start out at i = first_sg + 1. However, this is not correct since the first_sg could point to the sge sitting at slot MAX_SKB_FRAGS - 1, and a subsequent i = MAX_SKB_FRAGS will access the scatterlist ring (sg) out of bounds. Add the sk_msg_iter_var() helper for iterating through the ring, and apply the same rule for advancing to the next ring element as we do elsewhere. Later work will use this helper also in other places. Fixes: 015632bb30da ("bpf: sk_msg program helper bpf_sk_msg_pull_data") Signed-off-by: Daniel Borkmann Acked-by: John Fastabend --- net/core/filter.c | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 43ba5f8..2c7801f 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2282,6 +2282,13 @@ static const struct bpf_func_proto bpf_msg_cork_bytes_proto = { .arg2_type = ARG_ANYTHING, }; +#define sk_msg_iter_var(var) \ + do { \ + var++; \ + if (var == MAX_SKB_FRAGS) \ + var = 0; \ + } while (0) + BPF_CALL_4(bpf_msg_pull_data, struct sk_msg_buff *, msg, u32, start, u32, end, u64, flags) { @@ -2302,9 +2309,7 @@ BPF_CALL_4(bpf_msg_pull_data, if (start < offset + len) break; offset += len; - i++; - if (i == MAX_SKB_FRAGS) - i = 0; + sk_msg_iter_var(i); } while (i != msg->sg_end); if (unlikely(start >= offset + len)) @@ -2330,9 +2335,7 @@ BPF_CALL_4(bpf_msg_pull_data, */ do { copy += sg[i].length; - i++; - if (i == MAX_SKB_FRAGS) - i = 0; + sk_msg_iter_var(i); if (bytes_sg_total <= copy) break; } while (i != msg->sg_end); @@ -2358,9 +2361,7 @@ BPF_CALL_4(bpf_msg_pull_data, sg[i].length = 0; put_page(sg_page(&sg[i])); - i++; - if (i == MAX_SKB_FRAGS) - i = 0; + sk_msg_iter_var(i); } while (i != last_sg); sg[first_sg].length = copy; @@ -2377,7 +2378,8 @@ BPF_CALL_4(bpf_msg_pull_data, if (!shift) goto out; - i = first_sg + 1; + i = first_sg; + sk_msg_iter_var(i); do { int move_from; @@ -2394,9 +2396,7 @@ BPF_CALL_4(bpf_msg_pull_data, sg[move_from].page_link = 0; sg[move_from].offset = 0; - i++; - if (i == MAX_SKB_FRAGS) - i = 0; + sk_msg_iter_var(i); } while (1); msg->sg_end -= shift; if (msg->sg_end < 0) -- 2.9.5