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Subject[PATCH 4.18 051/168] bpf: Fix bpf_msg_pull_data()
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tushar Dave <tushar.n.dave@oracle.com>

[ Upstream commit 9db39f4d4f94b61e4b64b077f6ddb2bdfb533a88 ]

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 <tushar.n.dave@oracle.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/filter.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2282,7 +2282,7 @@ static const struct bpf_func_proto bpf_m
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;
@@ -2338,16 +2338,15 @@ 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]));


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