From 9db39f4d4f94b61e4b64b077f6ddb2bdfb533a88 Mon Sep 17 00:00:00 2001 From: Tushar Dave Date: Fri, 31 Aug 2018 23:45:16 +0200 Subject: [PATCH] bpf: Fix bpf_msg_pull_data() Helper bpf_msg_pull_data() mistakenly reuses variable 'offset' while linearizing multiple scatterlist elements. Variable 'offset' is used to find first starting scatterlist element i.e. msg->data = sg_virt(&sg[first_sg]) + start - offset" Use different variable name while linearizing multiple scatterlist elements so that value contained in variable 'offset' won't get overwritten. Fixes: 015632bb30da ("bpf: sk_msg program helper bpf_sk_msg_pull_data") Signed-off-by: Tushar Dave Signed-off-by: Daniel Borkmann --- net/core/filter.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 2c7801f6737a..aecdeba052d3 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2292,7 +2292,7 @@ static const struct bpf_func_proto bpf_msg_cork_bytes_proto = { 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, poffset = 0; int bytes = end - start, bytes_sg_total; struct scatterlist *sg = msg->sg_data; int first_sg, last_sg, i, shift; @@ -2348,16 +2348,15 @@ BPF_CALL_4(bpf_msg_pull_data, 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 + poffset; memcpy(to, from, len); - offset += len; + poffset += len; sg[i].length = 0; put_page(sg_page(&sg[i])); -- 2.34.1