From: Felix Maurer <fmaurer@xxxxxxxxxx> commit 4a11678f683814df82fca9018d964771e02d7e6d upstream. 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. Fixes: 6fff607e2f14b ("bpf: sk_msg program helper bpf_msg_push_data") Signed-off-by: Felix Maurer <fmaurer@xxxxxxxxxx> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Acked-by: Yonghong Song <yhs@xxxxxx> Acked-by: John Fastabend <john.fastabend@xxxxxxxxx> Link: https://lore.kernel.org/bpf/df69012695c7094ccb1943ca02b4920db3537466.1644421921.git.fmaurer@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/core/filter.c | 3 +++ 1 file changed, 3 insertions(+) --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2516,6 +2516,9 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_m if (unlikely(flags)) return -EINVAL; + if (unlikely(len == 0)) + return 0; + /* First find the starting scatterlist element */ i = msg->sg.start; do { Patches currently in stable-queue which might be from fmaurer@xxxxxxxxxx are queue-5.4/bpf-do-not-try-bpf_msg_push_data-with-len-0.patch