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Date: Thu, 30 Aug 2018 02:07:29 +0200
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: [PATCH net] ebpf: fix bpf_msg_pull_data
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;
--
1.8.3.1
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