From: Zijian Zhang <zijianzhang@xxxxxxxxxxxxx>
Found in the test_txmsg_pull in test_sockmap,
```
txmsg_cork = 512; // corking is importrant here
opt->iov_length = 3;
opt->iov_count = 1;
opt->rate = 512; // sendmsg will be invoked 512 times
```
The first sendmsg will send an sk_msg with size 3, and bpf_msg_pull_data
will be invoked the first time. sk_msg_reset_curr will reset the copybreak
from 3 to 0. In the second sendmsg, since we are in the stage of corking,
psock->cork will be reused in func sk_msg_alloc. msg->sg.copybreak is 0
now, the second msg will overwrite the first msg. As a result, we could
not pass the data integrity test.
The same problem happens in push and pop test. Thus, fix sk_msg_reset_curr
to restore the correct copybreak.
Fixes: bb9aefde5bba ("bpf: sockmap, updating the sg structure should also update curr")
Signed-off-by: Zijian Zhang <zijianzhang@xxxxxxxxxxxxx>
---
net/core/filter.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index fba445b96de8..00491ac4598f 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2619,18 +2619,16 @@ BPF_CALL_2(bpf_msg_cork_bytes, struct sk_msg *, msg, u32, bytes)
static void sk_msg_reset_curr(struct sk_msg *msg)
{
- u32 i = msg->sg.start;
- u32 len = 0;
-
- do {
- len += sk_msg_elem(msg, i)->length;
- sk_msg_iter_var_next(i);
- if (len >= msg->sg.size)
- break;
- } while (i != msg->sg.end);
+ if (!msg->sg.size) {
+ msg->sg.curr = msg->sg.start;
+ msg->sg.copybreak = 0;
+ } else {
+ u32 i = msg->sg.end;
- msg->sg.curr = i;
- msg->sg.copybreak = 0;
+ sk_msg_iter_var_prev(i);
+ msg->sg.curr = i;
+ msg->sg.copybreak = msg->sg.data[i].length;
+ }
}
static const struct bpf_func_proto bpf_msg_cork_bytes_proto = {
--
2.20.1
