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Commit 9db39f4d authored by Tushar Dave's avatar Tushar Dave Committed by Daniel Borkmann
Browse files

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: 015632bb ("bpf: sk_msg program helper bpf_sk_msg_pull_data")
Signed-off-by: default avatarTushar Dave <tushar.n.dave@oracle.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 93bbadd6

net/core/filter.c

+3 −4
Original line number Diff line number Diff line
@@ -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]));