If bpf_msg_push_data is called with len 0 (as it happens during
selftests/bpf/test_sockmap), we do not need to do anything and can
return early.
Calling bpf_msg_push_data with len 0 previously lead to a wrong ENOMEM
error: we later called get_order(copy + len); if len was 0, copy + len
was also often 0 and get_order returned some undefined value (at the
moment 52). alloc_pages caught that and failed, but then
bpf_msg_push_data returned ENOMEM. This was wrong because we are most
probably not out of memory and actually do not need any additional
memory.
v2: Add bug description and Fixes tag
Fixes: 6fff607e2f14b ("bpf: sk_msg program helper bpf_msg_push_data")
Signed-off-by: Felix Maurer <fmaurer@xxxxxxxxxx>
---
net/core/filter.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/core/filter.c b/net/core/filter.c
index 4603b7cd3cd1..9eb785842258 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2710,6 +2710,9 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
if (unlikely(flags))
return -EINVAL;
+ if (unlikely(len == 0))
+ return 0;
+
/* First find the starting scatterlist element */
i = msg->sg.start;
do {
--
2.34.1
